Question

ratinalise the denominator ​

Answer 1

Answer:

2-√5

2+√5

(2-√5)(2-√5)

(2+√5)(2-√5)

using

• (a-b)²=a²+b²-2ab
• (a+b)(a-b)=a²-b²

(2)²+(√5)²-2(2)(√5)

(2)²-(√5)²

4+5-4√5

4-5

9-4√5

-1

-(9-4√5) = 4√5-9

a√5+b=4√5+9

a=4

b=9

Answer 2

$\large{\sf{\underline{ANSWER}}}}$

• At first, We have to rationalise the denominator.

So,

$2-\sqrt{5}\frac{2}+{\sqrt{5}}+2-\sqrt{5}\frac{2}+{\sqrt{5}}$

$(2-\sqrt{5})^2\frac{1}$

$4-4\sqrt{5}+5$

$9-4\sqrt{5}=a\sqrt{5}+b$

$\sqrt{5} Will be cancel$

$a=-4 ,b=9$