Solve 6x^2-8x-35

$$6 x ^ { 2 } - 8 x - 35$$

Factor

$$6\left(x-\left(-\frac{\sqrt{226}}{6}+\frac{2}{3}\right)\right)\left(x-\left(\frac{\sqrt{226}}{6}+\frac{2}{3}\right)\right)$$

Steps Using the Quadratic Formula

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.

$$6x^{2}-8x-35=0$$

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.

$$x=\frac{-\left(-8\right)±\sqrt{\left(-8\right)^{2}-4\times 6\left(-35\right)}}{2\times 6}$$

Square -8.

$$x=\frac{-\left(-8\right)±\sqrt{64-4\times 6\left(-35\right)}}{2\times 6}$$

Multiply -4 times 6.

$$x=\frac{-\left(-8\right)±\sqrt{64-24\left(-35\right)}}{2\times 6}$$

Multiply -24 times -35.

$$x=\frac{-\left(-8\right)±\sqrt{64+840}}{2\times 6}$$

Add 64 to 840.

$$x=\frac{-\left(-8\right)±\sqrt{904}}{2\times 6}$$

Take the square root of 904.

$$x=\frac{-\left(-8\right)±2\sqrt{226}}{2\times 6}$$

The opposite of -8 is 8.

$$x=\frac{8±2\sqrt{226}}{2\times 6}$$

Multiply 2 times 6.

$$x=\frac{8±2\sqrt{226}}{12}$$

Now solve the equation x=\frac{8±2\sqrt{226}}{12} when ± is plus. Add 8 to 2\sqrt{226}.

$$x=\frac{2\sqrt{226}+8}{12}$$

Divide 8+2\sqrt{226} by 12.

$$x=\frac{\sqrt{226}}{6}+\frac{2}{3}$$

Now solve the equation x=\frac{8±2\sqrt{226}}{12} when ± is minus. Subtract 2\sqrt{226} from 8.

$$x=\frac{8-2\sqrt{226}}{12}$$

Divide 8-2\sqrt{226} by 12.

$$x=-\frac{\sqrt{226}}{6}+\frac{2}{3}$$

Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute \frac{2}{3}+\frac{\sqrt{226}}{6} for x_{1} and \frac{2}{3}-\frac{\sqrt{226}}{6} for x_{2}.

$$6x^{2}-8x-35=6\left(x-\left(\frac{\sqrt{226}}{6}+\frac{2}{3}\right)\right)\left(x-\left(-\frac{\sqrt{226}}{6}+\frac{2}{3}\right)\right)$$

Steps Using Direct Factoring Method

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.This is achieved by dividing both sides of the equation by 6

$$x ^ 2 -\frac{4}{3}x -\frac{35}{6} = 0$$

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

$$r + s = \frac{4}{3} rs = -\frac{35}{6}$$

Two numbers r and s sum up to \frac{4}{3} exactly when the average of the two numbers is \frac{1}{2}*\frac{4}{3} = \frac{2}{3}. 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>

$$r = \frac{2}{3} - u s = \frac{2}{3} + u$$

To solve for unknown quantity u, substitute these in the product equation rs = -\frac{35}{6}

$$(\frac{2}{3} - u) (\frac{2}{3} + u) = -\frac{35}{6}$$

Simplify by expanding (a -b) (a + b) = a^2 – b^2

$$\frac{4}{9} - u^2 = -\frac{35}{6}$$

Simplify the expression by subtracting \frac{4}{9} on both sides

$$-u^2 = -\frac{35}{6}-\frac{4}{9} = -\frac{113}{18}$$

Simplify the expression by multiplying -1 on both sides and take the square root to obtain the value of unknown variable u

$$u^2 = \frac{113}{18} u = \pm\sqrt{\frac{113}{18}} = \pm \frac{\sqrt{113}}{\sqrt{18}}$$

The factors r and s are the solutions to the quadratic equation. Substitute the value of u to compute the r and s.

$$r =\frac{2}{3} - \frac{\sqrt{113}}{\sqrt{18}} = -1.839 s = \frac{2}{3} + \frac{\sqrt{113}}{\sqrt{18}} = 3.172$$

Evaluate

$$6x^{2}-8x-35$$