Solve for x
x=-4
x = \frac{5}{2} = 2\frac{1}{2} = 2.5
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3x+6-\left(3x-6\right)\times 3=4\left(x-2\right)\left(x+2\right)
Variable x cannot be equal to any of the values -2,2 since division by zero is not defined. Multiply both sides of the equation by 3\left(x-2\right)\left(x+2\right), the least common multiple of x-2,x+2,3.
3x+6-\left(9x-18\right)=4\left(x-2\right)\left(x+2\right)
Use the distributive property to multiply 3x-6 by 3.
3x+6-9x+18=4\left(x-2\right)\left(x+2\right)
To find the opposite of 9x-18, find the opposite of each term.
-6x+6+18=4\left(x-2\right)\left(x+2\right)
Combine 3x and -9x to get -6x.
-6x+24=4\left(x-2\right)\left(x+2\right)
Add 6 and 18 to get 24.
-6x+24=\left(4x-8\right)\left(x+2\right)
Use the distributive property to multiply 4 by x-2.
-6x+24=4x^{2}-16
Use the distributive property to multiply 4x-8 by x+2 and combine like terms.
-6x+24-4x^{2}=-16
Subtract 4x^{2} from both sides.
-6x+24-4x^{2}+16=0
Add 16 to both sides.
-6x+40-4x^{2}=0
Add 24 and 16 to get 40.
-4x^{2}-6x+40=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{-\left(-6\right)±\sqrt{\left(-6\right)^{2}-4\left(-4\right)\times 40}}{2\left(-4\right)}
This equation is in standard form: ax^{2}+bx+c=0. Substitute -4 for a, -6 for b, and 40 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-\left(-6\right)±\sqrt{36-4\left(-4\right)\times 40}}{2\left(-4\right)}
Square -6.
x=\frac{-\left(-6\right)±\sqrt{36+16\times 40}}{2\left(-4\right)}
Multiply -4 times -4.
x=\frac{-\left(-6\right)±\sqrt{36+640}}{2\left(-4\right)}
Multiply 16 times 40.
x=\frac{-\left(-6\right)±\sqrt{676}}{2\left(-4\right)}
Add 36 to 640.
x=\frac{-\left(-6\right)±26}{2\left(-4\right)}
Take the square root of 676.
x=\frac{6±26}{2\left(-4\right)}
The opposite of -6 is 6.
x=\frac{6±26}{-8}
Multiply 2 times -4.
x=\frac{32}{-8}
Now solve the equation x=\frac{6±26}{-8} when ± is plus. Add 6 to 26.
x=-4
Divide 32 by -8.
x=-\frac{20}{-8}
Now solve the equation x=\frac{6±26}{-8} when ± is minus. Subtract 26 from 6.
x=\frac{5}{2}
Reduce the fraction \frac{-20}{-8} to lowest terms by extracting and canceling out 4.
x=-4 x=\frac{5}{2}
The equation is now solved.
3x+6-\left(3x-6\right)\times 3=4\left(x-2\right)\left(x+2\right)
Variable x cannot be equal to any of the values -2,2 since division by zero is not defined. Multiply both sides of the equation by 3\left(x-2\right)\left(x+2\right), the least common multiple of x-2,x+2,3.
3x+6-\left(9x-18\right)=4\left(x-2\right)\left(x+2\right)
Use the distributive property to multiply 3x-6 by 3.
3x+6-9x+18=4\left(x-2\right)\left(x+2\right)
To find the opposite of 9x-18, find the opposite of each term.
-6x+6+18=4\left(x-2\right)\left(x+2\right)
Combine 3x and -9x to get -6x.
-6x+24=4\left(x-2\right)\left(x+2\right)
Add 6 and 18 to get 24.
-6x+24=\left(4x-8\right)\left(x+2\right)
Use the distributive property to multiply 4 by x-2.
-6x+24=4x^{2}-16
Use the distributive property to multiply 4x-8 by x+2 and combine like terms.
-6x+24-4x^{2}=-16
Subtract 4x^{2} from both sides.
-6x-4x^{2}=-16-24
Subtract 24 from both sides.
-6x-4x^{2}=-40
Subtract 24 from -16 to get -40.
-4x^{2}-6x=-40
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}-6x}{-4}=-\frac{40}{-4}
Divide both sides by -4.
x^{2}+\left(-\frac{6}{-4}\right)x=-\frac{40}{-4}
Dividing by -4 undoes the multiplication by -4.
x^{2}+\frac{3}{2}x=-\frac{40}{-4}
Reduce the fraction \frac{-6}{-4} to lowest terms by extracting and canceling out 2.
x^{2}+\frac{3}{2}x=10
Divide -40 by -4.
x^{2}+\frac{3}{2}x+\left(\frac{3}{4}\right)^{2}=10+\left(\frac{3}{4}\right)^{2}
Divide \frac{3}{2}, the coefficient of the x term, by 2 to get \frac{3}{4}. Then add the square of \frac{3}{4} to both sides of the equation. This step makes the left hand side of the equation a perfect square.
x^{2}+\frac{3}{2}x+\frac{9}{16}=10+\frac{9}{16}
Square \frac{3}{4} by squaring both the numerator and the denominator of the fraction.
x^{2}+\frac{3}{2}x+\frac{9}{16}=\frac{169}{16}
Add 10 to \frac{9}{16}.
\left(x+\frac{3}{4}\right)^{2}=\frac{169}{16}
Factor x^{2}+\frac{3}{2}x+\frac{9}{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{3}{4}\right)^{2}}=\sqrt{\frac{169}{16}}
Take the square root of both sides of the equation.
x+\frac{3}{4}=\frac{13}{4} x+\frac{3}{4}=-\frac{13}{4}
Simplify.
x=\frac{5}{2} x=-4
Subtract \frac{3}{4} from both sides of the equation.
Examples
Quadratic equation
{ 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}