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4y^{2}+9+12y=0
Add 12y to both sides.
4y^{2}+12y+9=0
Rearrange the polynomial to put it in standard form. Place the terms in order from highest to lowest power.
a+b=12 ab=4\times 9=36
To solve the equation, factor the left hand side by grouping. First, left hand side needs to be rewritten as 4y^{2}+ay+by+9. To find a and b, set up a system to be solved.
1,36 2,18 3,12 4,9 6,6
Since ab is positive, a and b have the same sign. Since a+b is positive, a and b are both positive. List all such integer pairs that give product 36.
1+36=37 2+18=20 3+12=15 4+9=13 6+6=12
Calculate the sum for each pair.
a=6 b=6
The solution is the pair that gives sum 12.
\left(4y^{2}+6y\right)+\left(6y+9\right)
Rewrite 4y^{2}+12y+9 as \left(4y^{2}+6y\right)+\left(6y+9\right).
2y\left(2y+3\right)+3\left(2y+3\right)
Factor out 2y in the first and 3 in the second group.
\left(2y+3\right)\left(2y+3\right)
Factor out common term 2y+3 by using distributive property.
\left(2y+3\right)^{2}
Rewrite as a binomial square.
y=-\frac{3}{2}
To find equation solution, solve 2y+3=0.
4y^{2}+9+12y=0
Add 12y to both sides.
4y^{2}+12y+9=0
All equations of the form ax^{2}+bx+c=0 can be solved using the quadratic formula: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. The quadratic formula gives two solutions, one when ± is addition and one when it is subtraction.
y=\frac{-12±\sqrt{12^{2}-4\times 4\times 9}}{2\times 4}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 4 for a, 12 for b, and 9 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
y=\frac{-12±\sqrt{144-4\times 4\times 9}}{2\times 4}
Square 12.
y=\frac{-12±\sqrt{144-16\times 9}}{2\times 4}
Multiply -4 times 4.
y=\frac{-12±\sqrt{144-144}}{2\times 4}
Multiply -16 times 9.
y=\frac{-12±\sqrt{0}}{2\times 4}
Add 144 to -144.
y=-\frac{12}{2\times 4}
Take the square root of 0.
y=-\frac{12}{8}
Multiply 2 times 4.
y=-\frac{3}{2}
Reduce the fraction \frac{-12}{8} to lowest terms by extracting and canceling out 4.
4y^{2}+9+12y=0
Add 12y to both sides.
4y^{2}+12y=-9
Subtract 9 from both sides. Anything subtracted from zero gives its negation.
\frac{4y^{2}+12y}{4}=-\frac{9}{4}
Divide both sides by 4.
y^{2}+\frac{12}{4}y=-\frac{9}{4}
Dividing by 4 undoes the multiplication by 4.
y^{2}+3y=-\frac{9}{4}
Divide 12 by 4.
y^{2}+3y+\left(\frac{3}{2}\right)^{2}=-\frac{9}{4}+\left(\frac{3}{2}\right)^{2}
Divide 3, the coefficient of the x term, by 2 to get \frac{3}{2}. Then add the square of \frac{3}{2} to both sides of the equation. This step makes the left hand side of the equation a perfect square.
y^{2}+3y+\frac{9}{4}=\frac{-9+9}{4}
Square \frac{3}{2} by squaring both the numerator and the denominator of the fraction.
y^{2}+3y+\frac{9}{4}=0
Add -\frac{9}{4} to \frac{9}{4} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.
\left(y+\frac{3}{2}\right)^{2}=0
Factor y^{2}+3y+\frac{9}{4}. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.
\sqrt{\left(y+\frac{3}{2}\right)^{2}}=\sqrt{0}
Take the square root of both sides of the equation.
y+\frac{3}{2}=0 y+\frac{3}{2}=0
Simplify.
y=-\frac{3}{2} y=-\frac{3}{2}
Subtract \frac{3}{2} from both sides of the equation.
y=-\frac{3}{2}
The equation is now solved. Solutions are the same.