Solve for x
x=4
Graph
Share
Copied to clipboard
7\left(x+8\right)=4\times 21
Variable x cannot be equal to -8 since division by zero is not defined. Multiply both sides of the equation by 4\left(x+8\right), the least common multiple of 4,x+8.
7x+56=4\times 21
Use the distributive property to multiply 7 by x+8.
7x+56=84
Multiply 4 and 21 to get 84.
7x=84-56
Subtract 56 from both sides.
7x=28
Subtract 56 from 84 to get 28.
x=\frac{28}{7}
Divide both sides by 7.
x=4
Divide 28 by 7 to get 4.
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}