Answer:

Isolate the constant term c on one side of the equation.

Step-by-step explanation:

2d²+8d-10=0

2d²+8d=10                    isolate the constant by transposing 10

2d²/2+8d/2=10/2          since a=2, divide the equation by 2

d²+4d=5

d²+4d+(4/2)²=5+(4/2)²   in this step, always add (b/2)² on both sides

d²+4d+4=5+4

(d+2)²=9

d+2=±√9

d+2=+√9    ;     d+2= -√9

d=3-2                d= -3-2

d=1                    d= -5