Solve for r
r = -\frac{9}{2} = -4\frac{1}{2} = -4.5
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-2r-9=0
Combine -3r and r to get -2r.
-2r=9
Add 9 to both sides. Anything plus zero gives itself.
r=\frac{9}{-2}
Divide both sides by -2.
r=-\frac{9}{2}
Fraction \frac{9}{-2} can be rewritten as -\frac{9}{2} by extracting the negative sign.
Examples
Quadratic equation
{ x } ^ { 2 } - 4 x - 5 = 0
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4 \sin \theta \cos \theta = 2 \sin \theta
Linear equation
y = 3x + 4
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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
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Limits
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