Solve for x
x = \frac{21}{4} = 5\frac{1}{4} = 5.25
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4x+9-8x=-12
Subtract 8x from both sides.
-4x+9=-12
Combine 4x and -8x to get -4x.
-4x=-12-9
Subtract 9 from both sides.
-4x=-21
Subtract 9 from -12 to get -21.
x=\frac{-21}{-4}
Divide both sides by -4.
x=\frac{21}{4}
Fraction \frac{-21}{-4} can be simplified to \frac{21}{4} by removing the negative sign from both the numerator and the denominator.
Examples
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{ 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}