Factor
\left(x-\left(4-2\sqrt{3}\right)\right)\left(x-\left(2\sqrt{3}+4\right)\right)
Evaluate
x^{2}-8x+4
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x^{2}-8x+4=0
Quadratic polynomial can be factored using the transformation ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right), where x_{1} and x_{2} are the solutions of the quadratic equation ax^{2}+bx+c=0.
x=\frac{-\left(-8\right)±\sqrt{\left(-8\right)^{2}-4\times 4}}{2}
All equations of the form ax^{2}+bx+c=0 can be solved using the quadratic formula: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. The quadratic formula gives two solutions, one when ± is addition and one when it is subtraction.
x=\frac{-\left(-8\right)±\sqrt{64-4\times 4}}{2}
Square -8.
x=\frac{-\left(-8\right)±\sqrt{64-16}}{2}
Multiply -4 times 4.
x=\frac{-\left(-8\right)±\sqrt{48}}{2}
Add 64 to -16.
x=\frac{-\left(-8\right)±4\sqrt{3}}{2}
Take the square root of 48.
x=\frac{8±4\sqrt{3}}{2}
The opposite of -8 is 8.
x=\frac{4\sqrt{3}+8}{2}
Now solve the equation x=\frac{8±4\sqrt{3}}{2} when ± is plus. Add 8 to 4\sqrt{3}.
x=2\sqrt{3}+4
Divide 8+4\sqrt{3} by 2.
x=\frac{8-4\sqrt{3}}{2}
Now solve the equation x=\frac{8±4\sqrt{3}}{2} when ± is minus. Subtract 4\sqrt{3} from 8.
x=4-2\sqrt{3}
Divide 8-4\sqrt{3} by 2.
x^{2}-8x+4=\left(x-\left(2\sqrt{3}+4\right)\right)\left(x-\left(4-2\sqrt{3}\right)\right)
Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute 4+2\sqrt{3} for x_{1} and 4-2\sqrt{3} for x_{2}.
x ^ 2 -8x +4 = 0
Quadratic equations such as this one can be solved by a new direct factoring method that does not require guess work. To use the direct factoring method, the equation must be in the form x^2+Bx+C=0.
r + s = 8 rs = 4
Let r and s be the factors for the quadratic equation such that x^2+Bx+C=(x−r)(x−s) where sum of factors (r+s)=−B and the product of factors rs = C
r = 4 - u s = 4 + u
Two numbers r and s sum up to 8 exactly when the average of the two numbers is \frac{1}{2}*8 = 4. You can also see that the midpoint of r and s corresponds to the axis of symmetry of the parabola represented by the quadratic equation y=x^2+Bx+C. The values of r and s are equidistant from the center by an unknown quantity u. Express r and s with respect to variable u. <div style='padding: 8px'><img src='https://opalmath.azureedge.net/customsolver/quadraticgraph.png' style='width: 100%;max-width: 700px' /></div>
(4 - u) (4 + u) = 4
To solve for unknown quantity u, substitute these in the product equation rs = 4
16 - u^2 = 4
Simplify by expanding (a -b) (a + b) = a^2 – b^2
-u^2 = 4-16 = -12
Simplify the expression by subtracting 16 on both sides
u^2 = 12 u = \pm\sqrt{12} = \pm \sqrt{12}
Simplify the expression by multiplying -1 on both sides and take the square root to obtain the value of unknown variable u
r =4 - \sqrt{12} = 0.536 s = 4 + \sqrt{12} = 7.464
The factors r and s are the solutions to the quadratic equation. Substitute the value of u to compute the r and s.
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}