Question

If x² – 2x – 3 = 0; values of x correct to two significant figures are ______.

Options

• 3.0 and 1.0

• – 1.0 and 3.0

• 3.0 or – 1.0

• 3.00 or – 1.00

Answer 1

If x² – 2x – 3 = 0; values of x correct to two significant figures are 3.00 or – 1.00.

Explanation:

Given quadratic equation be

x² – 2x – 3 = 0   ...(1)

On comparing equation (1) with

ax² + bx + c = 0

We have a = 1; b = – 2 and c = – 3

Thus, by quadratic formula, we have

∴ `x = (-b ± sqrt(b^2 - 4ac))/(2a)`

= `(-(-2) ± sqrt((-2)^2 - 4 xx 1 xx (-3)))/(2 xx 1)`

= `(2 ± sqrt(4 + 12))/2`

= `(2 ± 4)/2`

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

= 3 or – 1

= 3.00 or – 1.00