51=(x+7)(x-7)

Solution for 51=(x+7)(x-7) equation:

Simplifying
51 = (x + 7)(x + -7)

Reorder the terms:
51 = (7 + x)(x + -7)

Reorder the terms:
51 = (7 + x)(-7 + x)

Multiply (7 + x) * (-7 + x)
51 = (7(-7 + x) + x(-7 + x))
51 = ((-7 * 7 + x * 7) + x(-7 + x))
51 = ((-49 + 7x) + x(-7 + x))
51 = (-49 + 7x + (-7 * x + x * x))
51 = (-49 + 7x + (-7x + x2))

Combine like terms: 7x + -7x = 0
51 = (-49 + 0 + x2)
51 = (-49 + x2)

Solving
51 = -49 + x2

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '-1x2' to each side of the equation.
51 + -1x2 = -49 + x2 + -1x2

Combine like terms: x2 + -1x2 = 0
51 + -1x2 = -49 + 0
51 + -1x2 = -49

Add '-51' to each side of the equation.
51 + -51 + -1x2 = -49 + -51

Combine like terms: 51 + -51 = 0
0 + -1x2 = -49 + -51
-1x2 = -49 + -51

Combine like terms: -49 + -51 = -100
-1x2 = -100

Divide each side by '-1'.
x2 = 100

Simplifying
x2 = 100

Take the square root of each side:
x = {-10, 10}