Question

X squared plus 2 x equals 15

x2+2x=15
what number should be added to both sides of the equation to complete the square?

Answer 1

Given

x 2 − 2 x = 15

add 1 to both sides to get:

6 = x 2 −

2 x + 1 = ( x − 1 ) 2

So x − 1 = ± √ 16 = ± 4

Add 1 to both sides to get:

x = 1 ± 4

That is: x = − 3

or

x = 5