Question

if x is 9-4√5, find the value of x square +1/x square​

Answer 1

$\huge\mathbb\green{ANSWER!!!!}$

Given -

• x = 9 - 4√5

then,

the value of

x² + 1/x is

• (9 - 4√5)² + 1/ (9-4√5)

• (9)² + (4√5)² - 2 × 9 × 4√5 + 1 / 9 - 4√5

• 81 + 80 - 72√5 + 1 / 9 - 4√5

• 162 - 72√5 / 9 - 4√5

Now, Rationalising the denominator -

• 162 - 72√5 / 9 - 4√5 × 9 + 4√5 / 9 + 4√5

• 1458 - 1440 / 81 - 80

• 18/1

• 18