Solve for x
x=-1
x=2
Graph
Share
Copied to clipboard
x+6-2x^{2}-x\left(x-2\right)=0
Use the distributive property to multiply 2-x by 2x+3 and combine like terms.
x+6-2x^{2}-\left(x^{2}-2x\right)=0
Use the distributive property to multiply x by x-2.
x+6-2x^{2}-x^{2}+2x=0
To find the opposite of x^{2}-2x, find the opposite of each term.
x+6-3x^{2}+2x=0
Combine -2x^{2} and -x^{2} to get -3x^{2}.
3x+6-3x^{2}=0
Combine x and 2x to get 3x.
x+2-x^{2}=0
Divide both sides by 3.
-x^{2}+x+2=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=-2
To solve the equation, factor the left hand side by grouping. First, left hand side needs to be rewritten as -x^{2}+ax+bx+2. To find a and b, set up a system to be solved.
a=2 b=-1
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. The only such pair is the system solution.
\left(-x^{2}+2x\right)+\left(-x+2\right)
Rewrite -x^{2}+x+2 as \left(-x^{2}+2x\right)+\left(-x+2\right).
-x\left(x-2\right)-\left(x-2\right)
Factor out -x in the first and -1 in the second group.
\left(x-2\right)\left(-x-1\right)
Factor out common term x-2 by using distributive property.
x=2 x=-1
To find equation solutions, solve x-2=0 and -x-1=0.
x+6-2x^{2}-x\left(x-2\right)=0
Use the distributive property to multiply 2-x by 2x+3 and combine like terms.
x+6-2x^{2}-\left(x^{2}-2x\right)=0
Use the distributive property to multiply x by x-2.
x+6-2x^{2}-x^{2}+2x=0
To find the opposite of x^{2}-2x, find the opposite of each term.
x+6-3x^{2}+2x=0
Combine -2x^{2} and -x^{2} to get -3x^{2}.
3x+6-3x^{2}=0
Combine x and 2x to get 3x.
-3x^{2}+3x+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{-3±\sqrt{3^{2}-4\left(-3\right)\times 6}}{2\left(-3\right)}
This equation is in standard form: ax^{2}+bx+c=0. Substitute -3 for a, 3 for b, and 6 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-3±\sqrt{9-4\left(-3\right)\times 6}}{2\left(-3\right)}
Square 3.
x=\frac{-3±\sqrt{9+12\times 6}}{2\left(-3\right)}
Multiply -4 times -3.
x=\frac{-3±\sqrt{9+72}}{2\left(-3\right)}
Multiply 12 times 6.
x=\frac{-3±\sqrt{81}}{2\left(-3\right)}
Add 9 to 72.
x=\frac{-3±9}{2\left(-3\right)}
Take the square root of 81.
x=\frac{-3±9}{-6}
Multiply 2 times -3.
x=\frac{6}{-6}
Now solve the equation x=\frac{-3±9}{-6} when ± is plus. Add -3 to 9.
x=-1
Divide 6 by -6.
x=-\frac{12}{-6}
Now solve the equation x=\frac{-3±9}{-6} when ± is minus. Subtract 9 from -3.
x=2
Divide -12 by -6.
x=-1 x=2
The equation is now solved.
x+6-2x^{2}-x\left(x-2\right)=0
Use the distributive property to multiply 2-x by 2x+3 and combine like terms.
x+6-2x^{2}-\left(x^{2}-2x\right)=0
Use the distributive property to multiply x by x-2.
x+6-2x^{2}-x^{2}+2x=0
To find the opposite of x^{2}-2x, find the opposite of each term.
x+6-3x^{2}+2x=0
Combine -2x^{2} and -x^{2} to get -3x^{2}.
3x+6-3x^{2}=0
Combine x and 2x to get 3x.
3x-3x^{2}=-6
Subtract 6 from both sides. Anything subtracted from zero gives its negation.
-3x^{2}+3x=-6
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{-3x^{2}+3x}{-3}=-\frac{6}{-3}
Divide both sides by -3.
x^{2}+\frac{3}{-3}x=-\frac{6}{-3}
Dividing by -3 undoes the multiplication by -3.
x^{2}-x=-\frac{6}{-3}
Divide 3 by -3.
x^{2}-x=2
Divide -6 by -3.
x^{2}-x+\left(-\frac{1}{2}\right)^{2}=2+\left(-\frac{1}{2}\right)^{2}
Divide -1, the coefficient of the x term, by 2 to get -\frac{1}{2}. Then add the square of -\frac{1}{2} to both sides of the equation. This step makes the left hand side of the equation a perfect square.
x^{2}-x+\frac{1}{4}=2+\frac{1}{4}
Square -\frac{1}{2} by squaring both the numerator and the denominator of the fraction.
x^{2}-x+\frac{1}{4}=\frac{9}{4}
Add 2 to \frac{1}{4}.
\left(x-\frac{1}{2}\right)^{2}=\frac{9}{4}
Factor x^{2}-x+\frac{1}{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{1}{2}\right)^{2}}=\sqrt{\frac{9}{4}}
Take the square root of both sides of the equation.
x-\frac{1}{2}=\frac{3}{2} x-\frac{1}{2}=-\frac{3}{2}
Simplify.
x=2 x=-1
Add \frac{1}{2} to 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}