Question

Using the quadratic formula to solve x2 = 5 – x, what are the values of x?

Answer 1

The answer will be A. -1+=
`√(21)`/2

Answer 2

A quadratic equation
`ax^2+bx+c = 0` ....[1] where, a, b and c are coefficient.

Then the solution is given by:

`x = -(b \pm √(b^2-4ac))/(2a)` ....[2]

As per the statement:

Given the equation:

`x^2=5-x`

⇒
`x^2+x-5 = 0`

On comparing with [1] we have;

a =1, b = 1 and c = -5

Then substitute these in [2] we have;

`x = (-1 \pm √(1^2-4(1)(-5)))/(2(1)) =(-1 \pm √(1+20))/(2) =(-1 \pm √(21))/(2)`

Therefore, the values of x are:

`x = (-1 + √(21))/(2)` ,
`(-1 - √(21))/(2)`