( x ^ { 2 } - 3 x - 2 = 0
Solve for x
x = \frac{\sqrt{17} + 3}{2} \approx 3.561552813
x=\frac{3-\sqrt{17}}{2}\approx -0.561552813
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x^{2}-3x-2=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(-3\right)±\sqrt{\left(-3\right)^{2}-4\left(-2\right)}}{2}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, -3 for b, and -2 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-\left(-3\right)±\sqrt{9-4\left(-2\right)}}{2}
Square -3.
x=\frac{-\left(-3\right)±\sqrt{9+8}}{2}
Multiply -4 times -2.
x=\frac{-\left(-3\right)±\sqrt{17}}{2}
Add 9 to 8.
x=\frac{3±\sqrt{17}}{2}
The opposite of -3 is 3.
x=\frac{\sqrt{17}+3}{2}
Now solve the equation x=\frac{3±\sqrt{17}}{2} when ± is plus. Add 3 to \sqrt{17}.
x=\frac{3-\sqrt{17}}{2}
Now solve the equation x=\frac{3±\sqrt{17}}{2} when ± is minus. Subtract \sqrt{17} from 3.
x=\frac{\sqrt{17}+3}{2} x=\frac{3-\sqrt{17}}{2}
The equation is now solved.
x^{2}-3x-2=0
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.
x^{2}-3x-2-\left(-2\right)=-\left(-2\right)
Add 2 to both sides of the equation.
x^{2}-3x=-\left(-2\right)
Subtracting -2 from itself leaves 0.
x^{2}-3x=2
Subtract -2 from 0.
x^{2}-3x+\left(-\frac{3}{2}\right)^{2}=2+\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}=2+\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{17}{4}
Add 2 to \frac{9}{4}.
\left(x-\frac{3}{2}\right)^{2}=\frac{17}{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{17}{4}}
Take the square root of both sides of the equation.
x-\frac{3}{2}=\frac{\sqrt{17}}{2} x-\frac{3}{2}=-\frac{\sqrt{17}}{2}
Simplify.
x=\frac{\sqrt{17}+3}{2} x=\frac{3-\sqrt{17}}{2}
Add \frac{3}{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}