(x+7)(x+9)=x^2+15x+42

Solution for (x+7)(x+9)=x^2+15x+42 equation:

Simplifying
(x + 7)(x + 9) = x2 + 15x + 42

Reorder the terms:
(7 + x)(x + 9) = x2 + 15x + 42

Reorder the terms:
(7 + x)(9 + x) = x2 + 15x + 42

Multiply (7 + x) * (9 + x)
(7(9 + x) + x(9 + x)) = x2 + 15x + 42
((9 * 7 + x * 7) + x(9 + x)) = x2 + 15x + 42
((63 + 7x) + x(9 + x)) = x2 + 15x + 42
(63 + 7x + (9 * x + x * x)) = x2 + 15x + 42
(63 + 7x + (9x + x2)) = x2 + 15x + 42

Combine like terms: 7x + 9x = 16x
(63 + 16x + x2) = x2 + 15x + 42

Reorder the terms:
63 + 16x + x2 = 42 + 15x + x2

Add '-1x2' to each side of the equation.
63 + 16x + x2 + -1x2 = 42 + 15x + x2 + -1x2

Combine like terms: x2 + -1x2 = 0
63 + 16x + 0 = 42 + 15x + x2 + -1x2
63 + 16x = 42 + 15x + x2 + -1x2

Combine like terms: x2 + -1x2 = 0
63 + 16x = 42 + 15x + 0
63 + 16x = 42 + 15x

Solving
63 + 16x = 42 + 15x

Solving for variable 'x'.

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

Add '-15x' to each side of the equation.
63 + 16x + -15x = 42 + 15x + -15x

Combine like terms: 16x + -15x = 1x
63 + 1x = 42 + 15x + -15x

Combine like terms: 15x + -15x = 0
63 + 1x = 42 + 0
63 + 1x = 42

Add '-63' to each side of the equation.
63 + -63 + 1x = 42 + -63

Combine like terms: 63 + -63 = 0
0 + 1x = 42 + -63
1x = 42 + -63

Combine like terms: 42 + -63 = -21
1x = -21

Divide each side by '1'.
x = -21

Simplifying
x = -21