b(b-4)=21

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Solution for b(b-4)=21 equation:


Simplifying
b(b + -4) = 21

Reorder the terms:
b(-4 + b) = 21
(-4 * b + b * b) = 21
(-4b + b2) = 21

Solving
-4b + b2 = 21

Solving for variable 'b'.

Reorder the terms:
-21 + -4b + b2 = 21 + -21

Combine like terms: 21 + -21 = 0
-21 + -4b + b2 = 0

Factor a trinomial.
(-3 + -1b)(7 + -1b) = 0

Subproblem 1

Set the factor '(-3 + -1b)' equal to zero and attempt to solve: Simplifying -3 + -1b = 0 Solving -3 + -1b = 0 Move all terms containing b to the left, all other terms to the right. Add '3' to each side of the equation. -3 + 3 + -1b = 0 + 3 Combine like terms: -3 + 3 = 0 0 + -1b = 0 + 3 -1b = 0 + 3 Combine like terms: 0 + 3 = 3 -1b = 3 Divide each side by '-1'. b = -3 Simplifying b = -3

Subproblem 2

Set the factor '(7 + -1b)' equal to zero and attempt to solve: Simplifying 7 + -1b = 0 Solving 7 + -1b = 0 Move all terms containing b to the left, all other terms to the right. Add '-7' to each side of the equation. 7 + -7 + -1b = 0 + -7 Combine like terms: 7 + -7 = 0 0 + -1b = 0 + -7 -1b = 0 + -7 Combine like terms: 0 + -7 = -7 -1b = -7 Divide each side by '-1'. b = 7 Simplifying b = 7

Solution

b = {-3, 7}

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