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18+\left(2x+4\right)x=24
Multiply both sides of the equation by 3.
18+2x^{2}+4x=24
Use the distributive property to multiply 2x+4 by x.
18+2x^{2}+4x-24=0
Subtract 24 from both sides.
-6+2x^{2}+4x=0
Subtract 24 from 18 to get -6.
2x^{2}+4x-6=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.
x=\frac{-4±\sqrt{4^{2}-4\times 2\left(-6\right)}}{2\times 2}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 2 for a, 4 for b, and -6 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-4±\sqrt{16-4\times 2\left(-6\right)}}{2\times 2}
Square 4.
x=\frac{-4±\sqrt{16-8\left(-6\right)}}{2\times 2}
Multiply -4 times 2.
x=\frac{-4±\sqrt{16+48}}{2\times 2}
Multiply -8 times -6.
x=\frac{-4±\sqrt{64}}{2\times 2}
Add 16 to 48.
x=\frac{-4±8}{2\times 2}
Take the square root of 64.
x=\frac{-4±8}{4}
Multiply 2 times 2.
x=\frac{4}{4}
Now solve the equation x=\frac{-4±8}{4} when ± is plus. Add -4 to 8.
x=1
Divide 4 by 4.
x=-\frac{12}{4}
Now solve the equation x=\frac{-4±8}{4} when ± is minus. Subtract 8 from -4.
x=-3
Divide -12 by 4.
x=1 x=-3
The equation is now solved.
18+\left(2x+4\right)x=24
Multiply both sides of the equation by 3.
18+2x^{2}+4x=24
Use the distributive property to multiply 2x+4 by x.
2x^{2}+4x=24-18
Subtract 18 from both sides.
2x^{2}+4x=6
Subtract 18 from 24 to get 6.
\frac{2x^{2}+4x}{2}=\frac{6}{2}
Divide both sides by 2.
x^{2}+\frac{4}{2}x=\frac{6}{2}
Dividing by 2 undoes the multiplication by 2.
x^{2}+2x=\frac{6}{2}
Divide 4 by 2.
x^{2}+2x=3
Divide 6 by 2.
x^{2}+2x+1^{2}=3+1^{2}
Divide 2, the coefficient of the x term, by 2 to get 1. Then add the square of 1 to both sides of the equation. This step makes the left hand side of the equation a perfect square.
x^{2}+2x+1=3+1
Square 1.
x^{2}+2x+1=4
Add 3 to 1.
\left(x+1\right)^{2}=4
Factor x^{2}+2x+1. 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(x+1\right)^{2}}=\sqrt{4}
Take the square root of both sides of the equation.
x+1=2 x+1=-2
Simplify.
x=1 x=-3
Subtract 1 from both sides of the equation.