Question

2.5.15

When given the equation - 23 = x² + 8x, a student says that you can add 64 to each side of the equation to complete the square. Is the student correct? If not,
describe and correct the error
r
u l in the anwar hoy to complete your choice

Answer 1

A student is incorrect, he should add 16, not 64.

Explanation:

Given the equation
`- 23 = x^2 + 8x`

To use formula

`(a+b)^2=a^2+2ab+b^2,`

note that

`8x=2\cdot x\cdot 4,`

so we need to add
`4^2=16` to complete the square

Therefore,

`-23+16=x^2+8x+16\\ \\-7=(x+4)^2`

A student is incorrect, he should add 16, not 64.