Solve for x
x=\frac{\sqrt{57}}{6}+\frac{1}{2}\approx 1.758305739
x=-\frac{\sqrt{57}}{6}+\frac{1}{2}\approx -0.758305739
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3x^{2}-3x=4
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.
3x^{2}-3x-4=4-4
Subtract 4 from both sides of the equation.
3x^{2}-3x-4=0
Subtracting 4 from itself leaves 0.
x=\frac{-\left(-3\right)±\sqrt{\left(-3\right)^{2}-4\times 3\left(-4\right)}}{2\times 3}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 3 for a, -3 for b, and -4 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-\left(-3\right)±\sqrt{9-4\times 3\left(-4\right)}}{2\times 3}
Square -3.
x=\frac{-\left(-3\right)±\sqrt{9-12\left(-4\right)}}{2\times 3}
Multiply -4 times 3.
x=\frac{-\left(-3\right)±\sqrt{9+48}}{2\times 3}
Multiply -12 times -4.
x=\frac{-\left(-3\right)±\sqrt{57}}{2\times 3}
Add 9 to 48.
x=\frac{3±\sqrt{57}}{2\times 3}
The opposite of -3 is 3.
x=\frac{3±\sqrt{57}}{6}
Multiply 2 times 3.
x=\frac{\sqrt{57}+3}{6}
Now solve the equation x=\frac{3±\sqrt{57}}{6} when ± is plus. Add 3 to \sqrt{57}.
x=\frac{\sqrt{57}}{6}+\frac{1}{2}
Divide 3+\sqrt{57} by 6.
x=\frac{3-\sqrt{57}}{6}
Now solve the equation x=\frac{3±\sqrt{57}}{6} when ± is minus. Subtract \sqrt{57} from 3.
x=-\frac{\sqrt{57}}{6}+\frac{1}{2}
Divide 3-\sqrt{57} by 6.
x=\frac{\sqrt{57}}{6}+\frac{1}{2} x=-\frac{\sqrt{57}}{6}+\frac{1}{2}
The equation is now solved.
3x^{2}-3x=4
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{4}{3}
Divide both sides by 3.
x^{2}+\left(-\frac{3}{3}\right)x=\frac{4}{3}
Dividing by 3 undoes the multiplication by 3.
x^{2}-x=\frac{4}{3}
Divide -3 by 3.
x^{2}-x+\left(-\frac{1}{2}\right)^{2}=\frac{4}{3}+\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}=\frac{4}{3}+\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{19}{12}
Add \frac{4}{3} to \frac{1}{4} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.
\left(x-\frac{1}{2}\right)^{2}=\frac{19}{12}
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{19}{12}}
Take the square root of both sides of the equation.
x-\frac{1}{2}=\frac{\sqrt{57}}{6} x-\frac{1}{2}=-\frac{\sqrt{57}}{6}
Simplify.
x=\frac{\sqrt{57}}{6}+\frac{1}{2} x=-\frac{\sqrt{57}}{6}+\frac{1}{2}
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}