-4x^2+16x=21

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Solution for -4x^2+16x=21 equation:


Simplifying
-4x2 + 16x = 21

Reorder the terms:
16x + -4x2 = 21

Solving
16x + -4x2 = 21

Solving for variable 'x'.

Reorder the terms:
-21 + 16x + -4x2 = 21 + -21

Combine like terms: 21 + -21 = 0
-21 + 16x + -4x2 = 0

Begin completing the square.  Divide all terms by
-4 the coefficient of the squared term: 

Divide each side by '-4'.
5.25 + -4x + x2 = 0

Move the constant term to the right:

Add '-5.25' to each side of the equation.
5.25 + -4x + -5.25 + x2 = 0 + -5.25

Reorder the terms:
5.25 + -5.25 + -4x + x2 = 0 + -5.25

Combine like terms: 5.25 + -5.25 = 0.00
0.00 + -4x + x2 = 0 + -5.25
-4x + x2 = 0 + -5.25

Combine like terms: 0 + -5.25 = -5.25
-4x + x2 = -5.25

The x term is -4x.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4x + 4 + x2 = -5.25 + 4

Reorder the terms:
4 + -4x + x2 = -5.25 + 4

Combine like terms: -5.25 + 4 = -1.25
4 + -4x + x2 = -1.25

Factor a perfect square on the left side:
(x + -2)(x + -2) = -1.25

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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