Evaluate
9-4\sqrt{5}\approx 0.05572809
Expand
9-4\sqrt{5}
Share
Copied to clipboard
4-4\sqrt{5}+\left(\sqrt{5}\right)^{2}
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(2-\sqrt{5}\right)^{2}.
4-4\sqrt{5}+5
The square of \sqrt{5} is 5.
9-4\sqrt{5}
Add 4 and 5 to get 9.
4-4\sqrt{5}+\left(\sqrt{5}\right)^{2}
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(2-\sqrt{5}\right)^{2}.
4-4\sqrt{5}+5
The square of \sqrt{5} is 5.
9-4\sqrt{5}
Add 4 and 5 to get 9.
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}