x(x+7)=15x-21

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Solution for x(x+7)=15x-21 equation:


Simplifying
x(x + 7) = 15x + -21

Reorder the terms:
x(7 + x) = 15x + -21
(7 * x + x * x) = 15x + -21
(7x + x2) = 15x + -21

Reorder the terms:
7x + x2 = -21 + 15x

Solving
7x + x2 = -21 + 15x

Solving for variable 'x'.

Reorder the terms:
21 + 7x + -15x + x2 = -21 + 15x + 21 + -15x

Combine like terms: 7x + -15x = -8x
21 + -8x + x2 = -21 + 15x + 21 + -15x

Reorder the terms:
21 + -8x + x2 = -21 + 21 + 15x + -15x

Combine like terms: -21 + 21 = 0
21 + -8x + x2 = 0 + 15x + -15x
21 + -8x + x2 = 15x + -15x

Combine like terms: 15x + -15x = 0
21 + -8x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + -8x + -21 + x2 = 0 + -21

Reorder the terms:
21 + -21 + -8x + x2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -8x + x2 = 0 + -21
-8x + x2 = 0 + -21

Combine like terms: 0 + -21 = -21
-8x + x2 = -21

The x term is -8x.  Take half its coefficient (-4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
-8x + 16 + x2 = -21 + 16

Reorder the terms:
16 + -8x + x2 = -21 + 16

Combine like terms: -21 + 16 = -5
16 + -8x + x2 = -5

Factor a perfect square on the left side:
(x + -4)(x + -4) = -5

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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