9y-4y(y+1)=31

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Solution for 9y-4y(y+1)=31 equation:


Simplifying
9y + -4y(y + 1) = 31

Reorder the terms:
9y + -4y(1 + y) = 31
9y + (1 * -4y + y * -4y) = 31
9y + (-4y + -4y2) = 31

Combine like terms: 9y + -4y = 5y
5y + -4y2 = 31

Solving
5y + -4y2 = 31

Solving for variable 'y'.

Reorder the terms:
-31 + 5y + -4y2 = 31 + -31

Combine like terms: 31 + -31 = 0
-31 + 5y + -4y2 = 0

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

Divide each side by '-4'.
7.75 + -1.25y + y2 = 0

Move the constant term to the right:

Add '-7.75' to each side of the equation.
7.75 + -1.25y + -7.75 + y2 = 0 + -7.75

Reorder the terms:
7.75 + -7.75 + -1.25y + y2 = 0 + -7.75

Combine like terms: 7.75 + -7.75 = 0.00
0.00 + -1.25y + y2 = 0 + -7.75
-1.25y + y2 = 0 + -7.75

Combine like terms: 0 + -7.75 = -7.75
-1.25y + y2 = -7.75

The y term is -1.25y.  Take half its coefficient (-0.625).
Square it (0.390625) and add it to both sides.

Add '0.390625' to each side of the equation.
-1.25y + 0.390625 + y2 = -7.75 + 0.390625

Reorder the terms:
0.390625 + -1.25y + y2 = -7.75 + 0.390625

Combine like terms: -7.75 + 0.390625 = -7.359375
0.390625 + -1.25y + y2 = -7.359375

Factor a perfect square on the left side:
(y + -0.625)(y + -0.625) = -7.359375

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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