Evaluate
2r\left(5-19r\right)
Expand
10r-38r^{2}
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2r^{2}-10r-5r\left(8r-4\right)
Use the distributive property to multiply 2r by r-5.
2r^{2}-10r-40r^{2}+20r
Use the distributive property to multiply -5r by 8r-4.
-38r^{2}-10r+20r
Combine 2r^{2} and -40r^{2} to get -38r^{2}.
-38r^{2}+10r
Combine -10r and 20r to get 10r.
2r^{2}-10r-5r\left(8r-4\right)
Use the distributive property to multiply 2r by r-5.
2r^{2}-10r-40r^{2}+20r
Use the distributive property to multiply -5r by 8r-4.
-38r^{2}-10r+20r
Combine 2r^{2} and -40r^{2} to get -38r^{2}.
-38r^{2}+10r
Combine -10r and 20r to get 10r.
Examples
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{ x } ^ { 2 } - 4 x - 5 = 0
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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}