Solve for x
x = \frac{2 \sqrt{21}}{3} \approx 3.055050463
x = -\frac{2 \sqrt{21}}{3} \approx -3.055050463
Graph
Share
Copied to clipboard
3x^{2}=7\times 4
Multiply both sides by 4.
3x^{2}=28
Multiply 7 and 4 to get 28.
x^{2}=\frac{28}{3}
Divide both sides by 3.
x=\frac{2\sqrt{21}}{3} x=-\frac{2\sqrt{21}}{3}
Take the square root of both sides of the equation.
3x^{2}=7\times 4
Multiply both sides by 4.
3x^{2}=28
Multiply 7 and 4 to get 28.
3x^{2}-28=0
Subtract 28 from both sides.
x=\frac{0±\sqrt{0^{2}-4\times 3\left(-28\right)}}{2\times 3}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 3 for a, 0 for b, and -28 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{0±\sqrt{-4\times 3\left(-28\right)}}{2\times 3}
Square 0.
x=\frac{0±\sqrt{-12\left(-28\right)}}{2\times 3}
Multiply -4 times 3.
x=\frac{0±\sqrt{336}}{2\times 3}
Multiply -12 times -28.
x=\frac{0±4\sqrt{21}}{2\times 3}
Take the square root of 336.
x=\frac{0±4\sqrt{21}}{6}
Multiply 2 times 3.
x=\frac{2\sqrt{21}}{3}
Now solve the equation x=\frac{0±4\sqrt{21}}{6} when ± is plus.
x=-\frac{2\sqrt{21}}{3}
Now solve the equation x=\frac{0±4\sqrt{21}}{6} when ± is minus.
x=\frac{2\sqrt{21}}{3} x=-\frac{2\sqrt{21}}{3}
The equation is now solved.
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}