(x+8)(x-1)=-21

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Solution for (x+8)(x-1)=-21 equation:


Simplifying
(x + 8)(x + -1) = -21

Reorder the terms:
(8 + x)(x + -1) = -21

Reorder the terms:
(8 + x)(-1 + x) = -21

Multiply (8 + x) * (-1 + x)
(8(-1 + x) + x(-1 + x)) = -21
((-1 * 8 + x * 8) + x(-1 + x)) = -21
((-8 + 8x) + x(-1 + x)) = -21
(-8 + 8x + (-1 * x + x * x)) = -21
(-8 + 8x + (-1x + x2)) = -21

Combine like terms: 8x + -1x = 7x
(-8 + 7x + x2) = -21

Solving
-8 + 7x + x2 = -21

Solving for variable 'x'.

Reorder the terms:
-8 + 21 + 7x + x2 = -21 + 21

Combine like terms: -8 + 21 = 13
13 + 7x + x2 = -21 + 21

Combine like terms: -21 + 21 = 0
13 + 7x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-13' to each side of the equation.
13 + 7x + -13 + x2 = 0 + -13

Reorder the terms:
13 + -13 + 7x + x2 = 0 + -13

Combine like terms: 13 + -13 = 0
0 + 7x + x2 = 0 + -13
7x + x2 = 0 + -13

Combine like terms: 0 + -13 = -13
7x + x2 = -13

The x term is 7x.  Take half its coefficient (3.5).
Square it (12.25) and add it to both sides.

Add '12.25' to each side of the equation.
7x + 12.25 + x2 = -13 + 12.25

Reorder the terms:
12.25 + 7x + x2 = -13 + 12.25

Combine like terms: -13 + 12.25 = -0.75
12.25 + 7x + x2 = -0.75

Factor a perfect square on the left side:
(x + 3.5)(x + 3.5) = -0.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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