Use quadratic formula solve. 7x^2 - 28x - 7

x = 2 + sqrt (5) or x = 2 - sqrt (5)

Step-by-step explanation using the quadratic formula:

Solve for x over the real numbers:

7 (x^2 - 4 x - 1) = 0

Divide both sides by 7:

x^2 - 4 x - 1 = 0

Add 1 to both sides:

x^2 - 4 x = 1

Add 4 to both sides:

x^2 - 4 x + 4 = 5

Write the left hand side as a square:

(x - 2) ^2 = 5

Take the square root of both sides:

x - 2 = sqrt (5) or x - 2 = - sqrt (5)

Add 2 to both sides:

x = 2 + sqrt (5) or x - 2 = - sqrt (5)

Add 2 to both sides:

Answer: x = 2 + sqrt (5) or x = 2 - sqrt (5)