Question

Solve 2x2 + 20x = −38.

Answer 1

2x^2+20x=-38  divide both sides by 2

x^2+10x=-19, halve the linear coefficient, square it, than add that value to both sides of the equation, in this case add (10/2)^2=25...

x^2+10x+25=6  now the left side is a perfect square

(x+5)^2=6  take the square root of both sides

x+5=±√6  subtract 5 from both sides

x=-5±√6    (so answer c.)