Solve for x
x\in \left(-1,2\right)
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x^{2}-x-2=0
To solve the inequality, factor the left hand side. Quadratic polynomial can be factored using the transformation ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right), where x_{1} and x_{2} are the solutions of the quadratic equation ax^{2}+bx+c=0.
x=\frac{-\left(-1\right)±\sqrt{\left(-1\right)^{2}-4\times 1\left(-2\right)}}{2}
All equations of the form ax^{2}+bx+c=0 can be solved using the quadratic formula: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. Substitute 1 for a, -1 for b, and -2 for c in the quadratic formula.
x=\frac{1±3}{2}
Do the calculations.
x=2 x=-1
Solve the equation x=\frac{1±3}{2} when ± is plus and when ± is minus.
\left(x-2\right)\left(x+1\right)<0
Rewrite the inequality by using the obtained solutions.
x-2>0 x+1<0
For the product to be negative, x-2 and x+1 have to be of the opposite signs. Consider the case when x-2 is positive and x+1 is negative.
x\in \emptyset
This is false for any x.
x+1>0 x-2<0
Consider the case when x+1 is positive and x-2 is negative.
x\in \left(-1,2\right)
The solution satisfying both inequalities is x\in \left(-1,2\right).
x\in \left(-1,2\right)
The final solution is the union of the obtained solutions.
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}