Question

If x² – 4x – 5 = 0, values of x correct to two decimal places are ______.

विकल्प

• 5.00 or – 1.00

• 5 or 1

• 5.0 and – 1.0

• – 5.00 and – 1.00

Answer 1

If x² – 4x – 5 = 0, values of x correct to two decimal places are 5.00 or – 1.00.

Explanation:

Given quadratic equation be,

x² – 4x – 5 = 0   ...(1)

On comparing equation (1) with

ax² + bx + c = 0

We have, a = 1; b = – 4 and c = – 5

By quadratic formula, we have

`x = (-b ± sqrt(b^2 - 4ac))/(2a)`

= `(-(-4) ± sqrt((-4)^2 - 4 xx 1 xx (-5)))/(2 xx 1)`

= `(4 ± sqrt(16 + 20))/2`

= `(4 ± 6)/2`

= `(4 + 6)/2` or `(4 - 6)/2`

= 5 or – 1

∴ x = 5.00 or – 1.00