Question

if x=4-√7 find x²-1
please give answer​

Answer 1

Answer:

8

Step-by-step explanation:

see attached image for the explanation

Answer 2

Answer:

22 - 8√7

Step-by-step explanation:

Given,

x = 4 - √7

To Find :-

x² - 1

How To Do :-

First we need to find value of 'x²'[By applying formula of (a - b)²] and we need to subtract 1 from it .

Formula Required :-

$(a-b)^2=a^2-2ab+b^2$

Solution :-

x² = ( 4 - √7)²

Comparing (a - b)² with (4 - √7)² :-

We can say , Values of :-

a = 4 , b = √7

→ (4 - √7)² = (4)² - 2(4)(√7) + (√7)²

= 16 - 8√7 + 7

= 23 - 8√7

x² - 1 = 23 - 8√7 - 1

= 22 - 8√7

∴ Value of 'x² - 1' = 22 - 8√7

Know More :-

Some Useful Algebraic formulas :-

1) (a + b)² = a² + 2ab + b²

2) (a - b)² = a² - 2ab + b²

3) (a + b) × (a - b) = a² - b²