5x^2 + 20x - 7 = 0
The first step to solve this using completing the square is to move the constant to the right. The constant is -7, so we will add 7 to both sides.
5x^ 2 + 20x = 7
Now we will divide the equation by 5. Because to complete the square, you must divide the equation by the coefficient of x^2.
x^2 + 4x = 7/5
Now we must figure out what to add to both sides to complete the square. To find that, you will half the coefficient of the x term and then square it. 4/2 = 2. 2^2=4. So we will add 4 to both sides.
x^2 + 4x + 4 = 7/5 + 4
Factor the left side.
(x + 2)^2 = 7/5 + 4
Calculate the right side.
(x + 2)^2 = 27/5
Now we will solve for x.
x = -3√(15)/5 -2
x = 3√(15)/5 -2
There are your two solutions. Hope this helped!