Question

87 ÷ 7- 2√5 find the value of this .
​

Answer 1

Step-by-step explanation:

i think it's helpful to you

Answer 2

Step-by-step explanation:

$\bf \underline{Solution-}$

$\textsf{Rationalising the denominator, we get}$

$\frac{87}{7 - 2 \sqrt{5} }$

$= \frac{87}{7 - 2 \sqrt{5} } \times \frac{7 + 2 \sqrt{5} }{7 + 2 \sqrt{5} }$

$= \frac{87(7 + 2 \sqrt{5} )}{(7 - 2 \sqrt{5})(7 + 2 \sqrt{5}) }$

$= \frac{87(7 + 2 \sqrt{5} )}{(7 {)}^{2} - (2 \sqrt{5} {)}^{2} }$

$= \frac{87(7 + 2 \sqrt{5} )}{49 - 20}$

$= \frac{87(7 + 2 \sqrt{5} )}{29}$

$= 3(7 + 2√5)$

$= 21 + 6 \sqrt{5}$

Hence, the denominator is rationalised.