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2x+12=4xx
Multiply both sides of the equation by 4.
2x+12=4x^{2}
Multiply x and x to get x^{2}.
2x+12-4x^{2}=0
Subtract 4x^{2} from both sides.
x+6-2x^{2}=0
Divide both sides by 2.
-2x^{2}+x+6=0
Rearrange the polynomial to put it in standard form. Place the terms in order from highest to lowest power.
a+b=1 ab=-2\times 6=-12
To solve the equation, factor the left hand side by grouping. First, left hand side needs to be rewritten as -2x^{2}+ax+bx+6. To find a and b, set up a system to be solved.
-1,12 -2,6 -3,4
Since ab is negative, a and b have the opposite signs. Since a+b is positive, the positive number has greater absolute value than the negative. List all such integer pairs that give product -12.
-1+12=11 -2+6=4 -3+4=1
Calculate the sum for each pair.
a=4 b=-3
The solution is the pair that gives sum 1.
\left(-2x^{2}+4x\right)+\left(-3x+6\right)
Rewrite -2x^{2}+x+6 as \left(-2x^{2}+4x\right)+\left(-3x+6\right).
2x\left(-x+2\right)+3\left(-x+2\right)
Factor out 2x in the first and 3 in the second group.
\left(-x+2\right)\left(2x+3\right)
Factor out common term -x+2 by using distributive property.
x=2 x=-\frac{3}{2}
To find equation solutions, solve -x+2=0 and 2x+3=0.
2x+12=4xx
Multiply both sides of the equation by 4.
2x+12=4x^{2}
Multiply x and x to get x^{2}.
2x+12-4x^{2}=0
Subtract 4x^{2} from both sides.
-4x^{2}+2x+12=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{-2±\sqrt{2^{2}-4\left(-4\right)\times 12}}{2\left(-4\right)}
This equation is in standard form: ax^{2}+bx+c=0. Substitute -4 for a, 2 for b, and 12 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-2±\sqrt{4-4\left(-4\right)\times 12}}{2\left(-4\right)}
Square 2.
x=\frac{-2±\sqrt{4+16\times 12}}{2\left(-4\right)}
Multiply -4 times -4.
x=\frac{-2±\sqrt{4+192}}{2\left(-4\right)}
Multiply 16 times 12.
x=\frac{-2±\sqrt{196}}{2\left(-4\right)}
Add 4 to 192.
x=\frac{-2±14}{2\left(-4\right)}
Take the square root of 196.
x=\frac{-2±14}{-8}
Multiply 2 times -4.
x=\frac{12}{-8}
Now solve the equation x=\frac{-2±14}{-8} when ± is plus. Add -2 to 14.
x=-\frac{3}{2}
Reduce the fraction \frac{12}{-8} to lowest terms by extracting and canceling out 4.
x=-\frac{16}{-8}
Now solve the equation x=\frac{-2±14}{-8} when ± is minus. Subtract 14 from -2.
x=2
Divide -16 by -8.
x=-\frac{3}{2} x=2
The equation is now solved.
2x+12=4xx
Multiply both sides of the equation by 4.
2x+12=4x^{2}
Multiply x and x to get x^{2}.
2x+12-4x^{2}=0
Subtract 4x^{2} from both sides.
2x-4x^{2}=-12
Subtract 12 from both sides. Anything subtracted from zero gives its negation.
-4x^{2}+2x=-12
Quadratic equations such as this one can be solved by completing the square. In order to complete the square, the equation must first be in the form x^{2}+bx=c.
\frac{-4x^{2}+2x}{-4}=-\frac{12}{-4}
Divide both sides by -4.
x^{2}+\frac{2}{-4}x=-\frac{12}{-4}
Dividing by -4 undoes the multiplication by -4.
x^{2}-\frac{1}{2}x=-\frac{12}{-4}
Reduce the fraction \frac{2}{-4} to lowest terms by extracting and canceling out 2.
x^{2}-\frac{1}{2}x=3
Divide -12 by -4.
x^{2}-\frac{1}{2}x+\left(-\frac{1}{4}\right)^{2}=3+\left(-\frac{1}{4}\right)^{2}
Divide -\frac{1}{2}, the coefficient of the x term, by 2 to get -\frac{1}{4}. Then add the square of -\frac{1}{4} to both sides of the equation. This step makes the left hand side of the equation a perfect square.
x^{2}-\frac{1}{2}x+\frac{1}{16}=3+\frac{1}{16}
Square -\frac{1}{4} by squaring both the numerator and the denominator of the fraction.
x^{2}-\frac{1}{2}x+\frac{1}{16}=\frac{49}{16}
Add 3 to \frac{1}{16}.
\left(x-\frac{1}{4}\right)^{2}=\frac{49}{16}
Factor x^{2}-\frac{1}{2}x+\frac{1}{16}. 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-\frac{1}{4}\right)^{2}}=\sqrt{\frac{49}{16}}
Take the square root of both sides of the equation.
x-\frac{1}{4}=\frac{7}{4} x-\frac{1}{4}=-\frac{7}{4}
Simplify.
x=2 x=-\frac{3}{2}
Add \frac{1}{4} to both sides of the equation.