Solve for x
x=6
x=-3
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2\left(x+3\right)\left(x-6\right)=0
Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.
\left(2x+6\right)\left(x-6\right)=0
Use the distributive property to multiply 2 by x+3.
2x^{2}-6x-36=0
Use the distributive property to multiply 2x+6 by x-6 and combine like terms.
x^{2}-3x-18=0
Divide both sides by 2.
a+b=-3 ab=1\left(-18\right)=-18
To solve the equation, factor the left hand side by grouping. First, left hand side needs to be rewritten as x^{2}+ax+bx-18. To find a and b, set up a system to be solved.
1,-18 2,-9 3,-6
Since ab is negative, a and b have the opposite signs. Since a+b is negative, the negative number has greater absolute value than the positive. List all such integer pairs that give product -18.
1-18=-17 2-9=-7 3-6=-3
Calculate the sum for each pair.
a=-6 b=3
The solution is the pair that gives sum -3.
\left(x^{2}-6x\right)+\left(3x-18\right)
Rewrite x^{2}-3x-18 as \left(x^{2}-6x\right)+\left(3x-18\right).
x\left(x-6\right)+3\left(x-6\right)
Factor out x in the first and 3 in the second group.
\left(x-6\right)\left(x+3\right)
Factor out common term x-6 by using distributive property.
x=6 x=-3
To find equation solutions, solve x-6=0 and x+3=0.
2\left(x+3\right)\left(x-6\right)=0
Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.
\left(2x+6\right)\left(x-6\right)=0
Use the distributive property to multiply 2 by x+3.
2x^{2}-6x-36=0
Use the distributive property to multiply 2x+6 by x-6 and combine like terms.
x=\frac{-\left(-6\right)±\sqrt{\left(-6\right)^{2}-4\times 2\left(-36\right)}}{2\times 2}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 2 for a, -6 for b, and -36 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-\left(-6\right)±\sqrt{36-4\times 2\left(-36\right)}}{2\times 2}
Square -6.
x=\frac{-\left(-6\right)±\sqrt{36-8\left(-36\right)}}{2\times 2}
Multiply -4 times 2.
x=\frac{-\left(-6\right)±\sqrt{36+288}}{2\times 2}
Multiply -8 times -36.
x=\frac{-\left(-6\right)±\sqrt{324}}{2\times 2}
Add 36 to 288.
x=\frac{-\left(-6\right)±18}{2\times 2}
Take the square root of 324.
x=\frac{6±18}{2\times 2}
The opposite of -6 is 6.
x=\frac{6±18}{4}
Multiply 2 times 2.
x=\frac{24}{4}
Now solve the equation x=\frac{6±18}{4} when ± is plus. Add 6 to 18.
x=6
Divide 24 by 4.
x=-\frac{12}{4}
Now solve the equation x=\frac{6±18}{4} when ± is minus. Subtract 18 from 6.
x=-3
Divide -12 by 4.
x=6 x=-3
The equation is now solved.
2\left(x+3\right)\left(x-6\right)=0
Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.
\left(2x+6\right)\left(x-6\right)=0
Use the distributive property to multiply 2 by x+3.
2x^{2}-6x-36=0
Use the distributive property to multiply 2x+6 by x-6 and combine like terms.
2x^{2}-6x=36
Add 36 to both sides. Anything plus zero gives itself.
\frac{2x^{2}-6x}{2}=\frac{36}{2}
Divide both sides by 2.
x^{2}+\left(-\frac{6}{2}\right)x=\frac{36}{2}
Dividing by 2 undoes the multiplication by 2.
x^{2}-3x=\frac{36}{2}
Divide -6 by 2.
x^{2}-3x=18
Divide 36 by 2.
x^{2}-3x+\left(-\frac{3}{2}\right)^{2}=18+\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.
x^{2}-3x+\frac{9}{4}=18+\frac{9}{4}
Square -\frac{3}{2} by squaring both the numerator and the denominator of the fraction.
x^{2}-3x+\frac{9}{4}=\frac{81}{4}
Add 18 to \frac{9}{4}.
\left(x-\frac{3}{2}\right)^{2}=\frac{81}{4}
Factor x^{2}-3x+\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(x-\frac{3}{2}\right)^{2}}=\sqrt{\frac{81}{4}}
Take the square root of both sides of the equation.
x-\frac{3}{2}=\frac{9}{2} x-\frac{3}{2}=-\frac{9}{2}
Simplify.
x=6 x=-3
Add \frac{3}{2} to both sides of the equation.
Examples
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{ x } ^ { 2 } - 4 x - 5 = 0
Trigonometry
4 \sin \theta \cos \theta = 2 \sin \theta
Linear equation
y = 3x + 4
Arithmetic
699 * 533
Matrix
\left[ \begin{array} { l l } { 2 } & { 3 } \\ { 5 } & { 4 } \end{array} \right] \left[ \begin{array} { l l l } { 2 } & { 0 } & { 3 } \\ { -1 } & { 1 } & { 5 } \end{array} \right]
Simultaneous equation
\left. \begin{cases} { 8x+2y = 46 } \\ { 7x+3y = 47 } \end{cases} \right.
Differentiation
\frac { d } { d x } \frac { ( 3 x ^ { 2 } - 2 ) } { ( x - 5 ) }
Integration
\int _ { 0 } ^ { 1 } x e ^ { - x ^ { 2 } } d x
Limits
\lim _{x \rightarrow-3} \frac{x^{2}-9}{x^{2}+2 x-3}