Skip to main content
Solve for x
Tick mark Image
Graph

Similar Problems from Web Search

Share

-3x+9=2\left(-x^{2}+2x+3\right)
Multiply both sides of the equation by 6, the least common multiple of 2,3.
-3x+9=2\left(-x^{2}\right)+4x+6
Use the distributive property to multiply 2 by -x^{2}+2x+3.
-3x+9-2\left(-x^{2}\right)=4x+6
Subtract 2\left(-x^{2}\right) from both sides.
-3x+9-2\left(-x^{2}\right)-4x=6
Subtract 4x from both sides.
-3x+9-2\left(-x^{2}\right)-4x-6=0
Subtract 6 from both sides.
-3x+9-2\left(-1\right)x^{2}-4x-6=0
Multiply -1 and 2 to get -2.
-3x+9+2x^{2}-4x-6=0
Multiply -2 and -1 to get 2.
-7x+9+2x^{2}-6=0
Combine -3x and -4x to get -7x.
-7x+3+2x^{2}=0
Subtract 6 from 9 to get 3.
2x^{2}-7x+3=0
Rearrange the polynomial to put it in standard form. Place the terms in order from highest to lowest power.
a+b=-7 ab=2\times 3=6
To solve the equation, factor the left hand side by grouping. First, left hand side needs to be rewritten as 2x^{2}+ax+bx+3. To find a and b, set up a system to be solved.
-1,-6 -2,-3
Since ab is positive, a and b have the same sign. Since a+b is negative, a and b are both negative. List all such integer pairs that give product 6.
-1-6=-7 -2-3=-5
Calculate the sum for each pair.
a=-6 b=-1
The solution is the pair that gives sum -7.
\left(2x^{2}-6x\right)+\left(-x+3\right)
Rewrite 2x^{2}-7x+3 as \left(2x^{2}-6x\right)+\left(-x+3\right).
2x\left(x-3\right)-\left(x-3\right)
Factor out 2x in the first and -1 in the second group.
\left(x-3\right)\left(2x-1\right)
Factor out common term x-3 by using distributive property.
x=3 x=\frac{1}{2}
To find equation solutions, solve x-3=0 and 2x-1=0.
-3x+9=2\left(-x^{2}+2x+3\right)
Multiply both sides of the equation by 6, the least common multiple of 2,3.
-3x+9=2\left(-x^{2}\right)+4x+6
Use the distributive property to multiply 2 by -x^{2}+2x+3.
-3x+9-2\left(-x^{2}\right)=4x+6
Subtract 2\left(-x^{2}\right) from both sides.
-3x+9-2\left(-x^{2}\right)-4x=6
Subtract 4x from both sides.
-3x+9-2\left(-x^{2}\right)-4x-6=0
Subtract 6 from both sides.
-3x+9-2\left(-1\right)x^{2}-4x-6=0
Multiply -1 and 2 to get -2.
-3x+9+2x^{2}-4x-6=0
Multiply -2 and -1 to get 2.
-7x+9+2x^{2}-6=0
Combine -3x and -4x to get -7x.
-7x+3+2x^{2}=0
Subtract 6 from 9 to get 3.
2x^{2}-7x+3=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(-7\right)±\sqrt{\left(-7\right)^{2}-4\times 2\times 3}}{2\times 2}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 2 for a, -7 for b, and 3 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-\left(-7\right)±\sqrt{49-4\times 2\times 3}}{2\times 2}
Square -7.
x=\frac{-\left(-7\right)±\sqrt{49-8\times 3}}{2\times 2}
Multiply -4 times 2.
x=\frac{-\left(-7\right)±\sqrt{49-24}}{2\times 2}
Multiply -8 times 3.
x=\frac{-\left(-7\right)±\sqrt{25}}{2\times 2}
Add 49 to -24.
x=\frac{-\left(-7\right)±5}{2\times 2}
Take the square root of 25.
x=\frac{7±5}{2\times 2}
The opposite of -7 is 7.
x=\frac{7±5}{4}
Multiply 2 times 2.
x=\frac{12}{4}
Now solve the equation x=\frac{7±5}{4} when ± is plus. Add 7 to 5.
x=3
Divide 12 by 4.
x=\frac{2}{4}
Now solve the equation x=\frac{7±5}{4} when ± is minus. Subtract 5 from 7.
x=\frac{1}{2}
Reduce the fraction \frac{2}{4} to lowest terms by extracting and canceling out 2.
x=3 x=\frac{1}{2}
The equation is now solved.
-3x+9=2\left(-x^{2}+2x+3\right)
Multiply both sides of the equation by 6, the least common multiple of 2,3.
-3x+9=2\left(-x^{2}\right)+4x+6
Use the distributive property to multiply 2 by -x^{2}+2x+3.
-3x+9-2\left(-x^{2}\right)=4x+6
Subtract 2\left(-x^{2}\right) from both sides.
-3x+9-2\left(-x^{2}\right)-4x=6
Subtract 4x from both sides.
-3x+9-2\left(-1\right)x^{2}-4x=6
Multiply -1 and 2 to get -2.
-3x+9+2x^{2}-4x=6
Multiply -2 and -1 to get 2.
-7x+9+2x^{2}=6
Combine -3x and -4x to get -7x.
-7x+2x^{2}=6-9
Subtract 9 from both sides.
-7x+2x^{2}=-3
Subtract 9 from 6 to get -3.
2x^{2}-7x=-3
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{2x^{2}-7x}{2}=-\frac{3}{2}
Divide both sides by 2.
x^{2}-\frac{7}{2}x=-\frac{3}{2}
Dividing by 2 undoes the multiplication by 2.
x^{2}-\frac{7}{2}x+\left(-\frac{7}{4}\right)^{2}=-\frac{3}{2}+\left(-\frac{7}{4}\right)^{2}
Divide -\frac{7}{2}, the coefficient of the x term, by 2 to get -\frac{7}{4}. Then add the square of -\frac{7}{4} to both sides of the equation. This step makes the left hand side of the equation a perfect square.
x^{2}-\frac{7}{2}x+\frac{49}{16}=-\frac{3}{2}+\frac{49}{16}
Square -\frac{7}{4} by squaring both the numerator and the denominator of the fraction.
x^{2}-\frac{7}{2}x+\frac{49}{16}=\frac{25}{16}
Add -\frac{3}{2} to \frac{49}{16} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.
\left(x-\frac{7}{4}\right)^{2}=\frac{25}{16}
Factor x^{2}-\frac{7}{2}x+\frac{49}{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{7}{4}\right)^{2}}=\sqrt{\frac{25}{16}}
Take the square root of both sides of the equation.
x-\frac{7}{4}=\frac{5}{4} x-\frac{7}{4}=-\frac{5}{4}
Simplify.
x=3 x=\frac{1}{2}
Add \frac{7}{4} to both sides of the equation.