Rationalizing denominators involving square roots and algebraic expressions.
A mathematical problem set featuring nine rational expressions with radicals in denominators, labeled (i) through (ix).
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Step-by-step solution for: RD Sharma Solutions Class 9 Maths Chapter 3 Rationalisation ...
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Show Answer Key & Explanations
Step-by-step solution for: RD Sharma Solutions Class 9 Maths Chapter 3 Rationalisation ...
It looks like you've uploaded an image containing a list of expressions that need to be rationalized — that is, simplified so that the denominator does not contain any radicals (square roots). These are typical algebra problems involving rationalizing denominators.
Let’s go through each one step by step. The goal is to eliminate radicals from the denominator using conjugates or other algebraic techniques.
---
Step: Multiply numerator and denominator by the conjugate $3 - \sqrt{2}$:
$$
\frac{1}{3 + \sqrt{2}} \cdot \frac{3 - \sqrt{2}}{3 - \sqrt{2}} = \frac{3 - \sqrt{2}}{(3)^2 - (\sqrt{2})^2} = \frac{3 - \sqrt{2}}{9 - 2} = \frac{3 - \sqrt{2}}{7}
$$
✔ Answer: $\boxed{\frac{3 - \sqrt{2}}{7}}$
---
Multiply by conjugate $\sqrt{6} + \sqrt{5}$:
$$
\frac{1}{\sqrt{6} - \sqrt{5}} \cdot \frac{\sqrt{6} + \sqrt{5}}{\sqrt{6} + \sqrt{5}} = \frac{\sqrt{6} + \sqrt{5}}{(\sqrt{6})^2 - (\sqrt{5})^2} = \frac{\sqrt{6} + \sqrt{5}}{6 - 5} = \sqrt{6} + \sqrt{5}
$$
✔ Answer: $\boxed{\sqrt{6} + \sqrt{5}}$
---
Multiply by conjugate $\sqrt{41} + 5$:
$$
\frac{16}{\sqrt{41} - 5} \cdot \frac{\sqrt{41} + 5}{\sqrt{41} + 5} = \frac{16(\sqrt{41} + 5)}{(\sqrt{41})^2 - (5)^2} = \frac{16(\sqrt{41} + 5)}{41 - 25} = \frac{16(\sqrt{41} + 5)}{16} = \sqrt{41} + 5
$$
✔ Answer: $\boxed{\sqrt{41} + 5}$
---
Factor denominator: $= \sqrt{3}(5) - \sqrt{5}(3)$
We can rationalize by multiplying numerator and denominator by the conjugate $5\sqrt{3} + 3\sqrt{5}$:
$$
\frac{30}{5\sqrt{3} - 3\sqrt{5}} \cdot \frac{5\sqrt{3} + 3\sqrt{5}}{5\sqrt{3} + 3\sqrt{5}} = \frac{30(5\sqrt{3} + 3\sqrt{5})}{(5\sqrt{3})^2 - (3\sqrt{5})^2}
$$
Compute denominator:
$$
(25 \cdot 3) - (9 \cdot 5) = 75 - 45 = 30
$$
So:
$$
\frac{30(5\sqrt{3} + 3\sqrt{5})}{30} = 5\sqrt{3} + 3\sqrt{5}
$$
✔ Answer: $\boxed{5\sqrt{3} + 3\sqrt{5}}$
---
Multiply by conjugate $2\sqrt{5} + \sqrt{3}$:
$$
\frac{1}{2\sqrt{5} - \sqrt{3}} \cdot \frac{2\sqrt{5} + \sqrt{3}}{2\sqrt{5} + \sqrt{3}} = \frac{2\sqrt{5} + \sqrt{3}}{(2\sqrt{5})^2 - (\sqrt{3})^2} = \frac{2\sqrt{5} + \sqrt{3}}{4 \cdot 5 - 3} = \frac{2\sqrt{5} + \sqrt{3}}{20 - 3} = \frac{2\sqrt{5} + \sqrt{3}}{17}
$$
✔ Answer: $\boxed{\frac{2\sqrt{5} + \sqrt{3}}{17}}$
---
Multiply numerator and denominator by conjugate $2\sqrt{2} + \sqrt{3}$:
$$
\frac{\sqrt{3} + 1}{2\sqrt{2} - \sqrt{3}} \cdot \frac{2\sqrt{2} + \sqrt{3}}{2\sqrt{2} + \sqrt{3}} = \frac{(\sqrt{3} + 1)(2\sqrt{2} + \sqrt{3})}{(2\sqrt{2})^2 - (\sqrt{3})^2}
$$
Denominator:
$$
8 - 3 = 5
$$
Numerator:
$$
(\sqrt{3})(2\sqrt{2}) + (\sqrt{3})(\sqrt{3}) + (1)(2\sqrt{2}) + (1)(\sqrt{3}) = 2\sqrt{6} + 3 + 2\sqrt{2} + \sqrt{3}
$$
So:
$$
\frac{2\sqrt{6} + 2\sqrt{2} + \sqrt{3} + 3}{5}
$$
✔ Answer: $\boxed{\frac{2\sqrt{6} + 2\sqrt{2} + \sqrt{3} + 3}{5}}$
---
This is a fraction with radical in both numerator and denominator. Rationalize by multiplying numerator and denominator by the conjugate $6 - 4\sqrt{2}$:
Wait — actually, the denominator is $6 + 4\sqrt{2}$, so conjugate is $6 - 4\sqrt{2}$:
$$
\frac{6 - 4\sqrt{2}}{6 + 4\sqrt{2}} \cdot \frac{6 - 4\sqrt{2}}{6 - 4\sqrt{2}} = \frac{(6 - 4\sqrt{2})^2}{(6)^2 - (4\sqrt{2})^2}
$$
Numerator:
$$
(6)^2 - 2 \cdot 6 \cdot 4\sqrt{2} + (4\sqrt{2})^2 = 36 - 48\sqrt{2} + 16 \cdot 2 = 36 - 48\sqrt{2} + 32 = 68 - 48\sqrt{2}
$$
Denominator:
$$
36 - (16 \cdot 2) = 36 - 32 = 4
$$
So:
$$
\frac{68 - 48\sqrt{2}}{4} = 17 - 12\sqrt{2}
$$
✔ Answer: $\boxed{17 - 12\sqrt{2}}$
---
Multiply by conjugate $2\sqrt{5} + 3$:
$$
\frac{3\sqrt{2} + 1}{2\sqrt{5} - 3} \cdot \frac{2\sqrt{5} + 3}{2\sqrt{5} + 3} = \frac{(3\sqrt{2} + 1)(2\sqrt{5} + 3)}{(2\sqrt{5})^2 - (3)^2}
$$
Denominator:
$$
4 \cdot 5 - 9 = 20 - 9 = 11
$$
Numerator:
$$
3\sqrt{2} \cdot 2\sqrt{5} = 6\sqrt{10},\quad 3\sqrt{2} \cdot 3 = 9\sqrt{2},\quad 1 \cdot 2\sqrt{5} = 2\sqrt{5},\quad 1 \cdot 3 = 3
$$
So total numerator: $6\sqrt{10} + 9\sqrt{2} + 2\sqrt{5} + 3$
Thus:
$$
\frac{6\sqrt{10} + 9\sqrt{2} + 2\sqrt{5} + 3}{11}
$$
✔ Answer: $\boxed{\frac{6\sqrt{10} + 9\sqrt{2} + 2\sqrt{5} + 3}{11}}$
---
This one is trickier. We want to rationalize the denominator.
Multiply numerator and denominator by the conjugate $\sqrt{a^2 + b^2} - a$:
$$
\frac{b^2}{\sqrt{a^2 + b^2} + a} \cdot \frac{\sqrt{a^2 + b^2} - a}{\sqrt{a^2 + b^2} - a} = \frac{b^2(\sqrt{a^2 + b^2} - a)}{(\sqrt{a^2 + b^2})^2 - a^2}
$$
Denominator:
$$
(a^2 + b^2) - a^2 = b^2
$$
So:
$$
\frac{b^2(\sqrt{a^2 + b^2} - a)}{b^2} = \sqrt{a^2 + b^2} - a
$$
✔ Answer: $\boxed{\sqrt{a^2 + b^2} - a}$
---
| Problem | Answer |
|--------|--------|
| (i) | $\frac{3 - \sqrt{2}}{7}$ |
| (ii) | $\sqrt{6} + \sqrt{5}$ |
| (iii) | $\sqrt{41} + 5$ |
| (iv) | $5\sqrt{3} + 3\sqrt{5}$ |
| (v) | $\frac{2\sqrt{5} + \sqrt{3}}{17}$ |
| (vi) | $\frac{2\sqrt{6} + 2\sqrt{2} + \sqrt{3} + 3}{5}$ |
| (vii) | $17 - 12\sqrt{2}$ |
| (viii) | $\frac{6\sqrt{10} + 9\sqrt{2} + 2\sqrt{5} + 3}{11}$ |
| (ix) | $\sqrt{a^2 + b^2} - a$ |
Let me know if you'd like these explained further or formatted differently!
Let’s go through each one step by step. The goal is to eliminate radicals from the denominator using conjugates or other algebraic techniques.
---
(i) $\frac{1}{3 + \sqrt{2}}$
Step: Multiply numerator and denominator by the conjugate $3 - \sqrt{2}$:
$$
\frac{1}{3 + \sqrt{2}} \cdot \frac{3 - \sqrt{2}}{3 - \sqrt{2}} = \frac{3 - \sqrt{2}}{(3)^2 - (\sqrt{2})^2} = \frac{3 - \sqrt{2}}{9 - 2} = \frac{3 - \sqrt{2}}{7}
$$
✔ Answer: $\boxed{\frac{3 - \sqrt{2}}{7}}$
---
(ii) $\frac{1}{\sqrt{6} - \sqrt{5}}$
Multiply by conjugate $\sqrt{6} + \sqrt{5}$:
$$
\frac{1}{\sqrt{6} - \sqrt{5}} \cdot \frac{\sqrt{6} + \sqrt{5}}{\sqrt{6} + \sqrt{5}} = \frac{\sqrt{6} + \sqrt{5}}{(\sqrt{6})^2 - (\sqrt{5})^2} = \frac{\sqrt{6} + \sqrt{5}}{6 - 5} = \sqrt{6} + \sqrt{5}
$$
✔ Answer: $\boxed{\sqrt{6} + \sqrt{5}}$
---
(iii) $\frac{16}{\sqrt{41} - 5}$
Multiply by conjugate $\sqrt{41} + 5$:
$$
\frac{16}{\sqrt{41} - 5} \cdot \frac{\sqrt{41} + 5}{\sqrt{41} + 5} = \frac{16(\sqrt{41} + 5)}{(\sqrt{41})^2 - (5)^2} = \frac{16(\sqrt{41} + 5)}{41 - 25} = \frac{16(\sqrt{41} + 5)}{16} = \sqrt{41} + 5
$$
✔ Answer: $\boxed{\sqrt{41} + 5}$
---
(iv) $\frac{30}{5\sqrt{3} - 3\sqrt{5}}$
Factor denominator: $= \sqrt{3}(5) - \sqrt{5}(3)$
We can rationalize by multiplying numerator and denominator by the conjugate $5\sqrt{3} + 3\sqrt{5}$:
$$
\frac{30}{5\sqrt{3} - 3\sqrt{5}} \cdot \frac{5\sqrt{3} + 3\sqrt{5}}{5\sqrt{3} + 3\sqrt{5}} = \frac{30(5\sqrt{3} + 3\sqrt{5})}{(5\sqrt{3})^2 - (3\sqrt{5})^2}
$$
Compute denominator:
$$
(25 \cdot 3) - (9 \cdot 5) = 75 - 45 = 30
$$
So:
$$
\frac{30(5\sqrt{3} + 3\sqrt{5})}{30} = 5\sqrt{3} + 3\sqrt{5}
$$
✔ Answer: $\boxed{5\sqrt{3} + 3\sqrt{5}}$
---
(v) $\frac{1}{2\sqrt{5} - \sqrt{3}}$
Multiply by conjugate $2\sqrt{5} + \sqrt{3}$:
$$
\frac{1}{2\sqrt{5} - \sqrt{3}} \cdot \frac{2\sqrt{5} + \sqrt{3}}{2\sqrt{5} + \sqrt{3}} = \frac{2\sqrt{5} + \sqrt{3}}{(2\sqrt{5})^2 - (\sqrt{3})^2} = \frac{2\sqrt{5} + \sqrt{3}}{4 \cdot 5 - 3} = \frac{2\sqrt{5} + \sqrt{3}}{20 - 3} = \frac{2\sqrt{5} + \sqrt{3}}{17}
$$
✔ Answer: $\boxed{\frac{2\sqrt{5} + \sqrt{3}}{17}}$
---
(vi) $\frac{\sqrt{3} + 1}{2\sqrt{2} - \sqrt{3}}$
Multiply numerator and denominator by conjugate $2\sqrt{2} + \sqrt{3}$:
$$
\frac{\sqrt{3} + 1}{2\sqrt{2} - \sqrt{3}} \cdot \frac{2\sqrt{2} + \sqrt{3}}{2\sqrt{2} + \sqrt{3}} = \frac{(\sqrt{3} + 1)(2\sqrt{2} + \sqrt{3})}{(2\sqrt{2})^2 - (\sqrt{3})^2}
$$
Denominator:
$$
8 - 3 = 5
$$
Numerator:
$$
(\sqrt{3})(2\sqrt{2}) + (\sqrt{3})(\sqrt{3}) + (1)(2\sqrt{2}) + (1)(\sqrt{3}) = 2\sqrt{6} + 3 + 2\sqrt{2} + \sqrt{3}
$$
So:
$$
\frac{2\sqrt{6} + 2\sqrt{2} + \sqrt{3} + 3}{5}
$$
✔ Answer: $\boxed{\frac{2\sqrt{6} + 2\sqrt{2} + \sqrt{3} + 3}{5}}$
---
(vii) $\frac{6 - 4\sqrt{2}}{6 + 4\sqrt{2}}$
This is a fraction with radical in both numerator and denominator. Rationalize by multiplying numerator and denominator by the conjugate $6 - 4\sqrt{2}$:
Wait — actually, the denominator is $6 + 4\sqrt{2}$, so conjugate is $6 - 4\sqrt{2}$:
$$
\frac{6 - 4\sqrt{2}}{6 + 4\sqrt{2}} \cdot \frac{6 - 4\sqrt{2}}{6 - 4\sqrt{2}} = \frac{(6 - 4\sqrt{2})^2}{(6)^2 - (4\sqrt{2})^2}
$$
Numerator:
$$
(6)^2 - 2 \cdot 6 \cdot 4\sqrt{2} + (4\sqrt{2})^2 = 36 - 48\sqrt{2} + 16 \cdot 2 = 36 - 48\sqrt{2} + 32 = 68 - 48\sqrt{2}
$$
Denominator:
$$
36 - (16 \cdot 2) = 36 - 32 = 4
$$
So:
$$
\frac{68 - 48\sqrt{2}}{4} = 17 - 12\sqrt{2}
$$
✔ Answer: $\boxed{17 - 12\sqrt{2}}$
---
(viii) $\frac{3\sqrt{2} + 1}{2\sqrt{5} - 3}$
Multiply by conjugate $2\sqrt{5} + 3$:
$$
\frac{3\sqrt{2} + 1}{2\sqrt{5} - 3} \cdot \frac{2\sqrt{5} + 3}{2\sqrt{5} + 3} = \frac{(3\sqrt{2} + 1)(2\sqrt{5} + 3)}{(2\sqrt{5})^2 - (3)^2}
$$
Denominator:
$$
4 \cdot 5 - 9 = 20 - 9 = 11
$$
Numerator:
$$
3\sqrt{2} \cdot 2\sqrt{5} = 6\sqrt{10},\quad 3\sqrt{2} \cdot 3 = 9\sqrt{2},\quad 1 \cdot 2\sqrt{5} = 2\sqrt{5},\quad 1 \cdot 3 = 3
$$
So total numerator: $6\sqrt{10} + 9\sqrt{2} + 2\sqrt{5} + 3$
Thus:
$$
\frac{6\sqrt{10} + 9\sqrt{2} + 2\sqrt{5} + 3}{11}
$$
✔ Answer: $\boxed{\frac{6\sqrt{10} + 9\sqrt{2} + 2\sqrt{5} + 3}{11}}$
---
(ix) $\frac{b^2}{\sqrt{a^2 + b^2} + a}$
This one is trickier. We want to rationalize the denominator.
Multiply numerator and denominator by the conjugate $\sqrt{a^2 + b^2} - a$:
$$
\frac{b^2}{\sqrt{a^2 + b^2} + a} \cdot \frac{\sqrt{a^2 + b^2} - a}{\sqrt{a^2 + b^2} - a} = \frac{b^2(\sqrt{a^2 + b^2} - a)}{(\sqrt{a^2 + b^2})^2 - a^2}
$$
Denominator:
$$
(a^2 + b^2) - a^2 = b^2
$$
So:
$$
\frac{b^2(\sqrt{a^2 + b^2} - a)}{b^2} = \sqrt{a^2 + b^2} - a
$$
✔ Answer: $\boxed{\sqrt{a^2 + b^2} - a}$
---
✔ Final Answers Summary:
| Problem | Answer |
|--------|--------|
| (i) | $\frac{3 - \sqrt{2}}{7}$ |
| (ii) | $\sqrt{6} + \sqrt{5}$ |
| (iii) | $\sqrt{41} + 5$ |
| (iv) | $5\sqrt{3} + 3\sqrt{5}$ |
| (v) | $\frac{2\sqrt{5} + \sqrt{3}}{17}$ |
| (vi) | $\frac{2\sqrt{6} + 2\sqrt{2} + \sqrt{3} + 3}{5}$ |
| (vii) | $17 - 12\sqrt{2}$ |
| (viii) | $\frac{6\sqrt{10} + 9\sqrt{2} + 2\sqrt{5} + 3}{11}$ |
| (ix) | $\sqrt{a^2 + b^2} - a$ |
Let me know if you'd like these explained further or formatted differently!
Parent Tip: Review the logic above to help your child master the concept of rationalize denominator worksheet.