5b(-b+3)=21

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Solution for 5b(-b+3)=21 equation:


Simplifying
5b(-1b + 3) = 21

Reorder the terms:
5b(3 + -1b) = 21
(3 * 5b + -1b * 5b) = 21
(15b + -5b2) = 21

Solving
15b + -5b2 = 21

Solving for variable 'b'.

Reorder the terms:
-21 + 15b + -5b2 = 21 + -21

Combine like terms: 21 + -21 = 0
-21 + 15b + -5b2 = 0

Begin completing the square.  Divide all terms by
-5 the coefficient of the squared term: 

Divide each side by '-5'.
4.2 + -3b + b2 = 0

Move the constant term to the right:

Add '-4.2' to each side of the equation.
4.2 + -3b + -4.2 + b2 = 0 + -4.2

Reorder the terms:
4.2 + -4.2 + -3b + b2 = 0 + -4.2

Combine like terms: 4.2 + -4.2 = 0.0
0.0 + -3b + b2 = 0 + -4.2
-3b + b2 = 0 + -4.2

Combine like terms: 0 + -4.2 = -4.2
-3b + b2 = -4.2

The b term is -3b.  Take half its coefficient (-1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
-3b + 2.25 + b2 = -4.2 + 2.25

Reorder the terms:
2.25 + -3b + b2 = -4.2 + 2.25

Combine like terms: -4.2 + 2.25 = -1.95
2.25 + -3b + b2 = -1.95

Factor a perfect square on the left side:
(b + -1.5)(b + -1.5) = -1.95

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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