Solve 14x^2+x-14

$$14 x ^ { 2 } + x - 14$$

Factor

$$14\left(x-\frac{-\sqrt{785}-1}{28}\right)\left(x-\frac{\sqrt{785}-1}{28}\right)$$

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.

$$14x^{2}+x-14=0$$

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.

$$x=\frac{-1±\sqrt{1^{2}-4\times 14\left(-14\right)}}{2\times 14}$$

Square 1.

$$x=\frac{-1±\sqrt{1-4\times 14\left(-14\right)}}{2\times 14}$$

Multiply -4 times 14.

$$x=\frac{-1±\sqrt{1-56\left(-14\right)}}{2\times 14}$$

Multiply -56 times -14.

$$x=\frac{-1±\sqrt{1+784}}{2\times 14}$$

Add 1 to 784.

$$x=\frac{-1±\sqrt{785}}{2\times 14}$$

Multiply 2 times 14.

$$x=\frac{-1±\sqrt{785}}{28}$$

Now solve the equation x=\frac{-1±\sqrt{785}}{28} when ± is plus. Add -1 to \sqrt{785}.

$$x=\frac{\sqrt{785}-1}{28}$$

Now solve the equation x=\frac{-1±\sqrt{785}}{28} when ± is minus. Subtract \sqrt{785} from -1.

$$x=\frac{-\sqrt{785}-1}{28}$$

Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute \frac{-1+\sqrt{785}}{28} for x_{1} and \frac{-1-\sqrt{785}}{28} for x_{2}.

$$14x^{2}+x-14=14\left(x-\frac{\sqrt{785}-1}{28}\right)\left(x-\frac{-\sqrt{785}-1}{28}\right)$$

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 14

$$x ^ 2 +\frac{1}{14}x -1 = 0$$

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

$$r + s = -\frac{1}{14} rs = -1$$

Two numbers r and s sum up to -\frac{1}{14} exactly when the average of the two numbers is \frac{1}{2}*-\frac{1}{14} = -\frac{1}{28}. 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>

$$r = -\frac{1}{28} - u s = -\frac{1}{28} + u$$

To solve for unknown quantity u, substitute these in the product equation rs = -1

$$(-\frac{1}{28} - u) (-\frac{1}{28} + u) = -1$$

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

$$\frac{1}{784} - u^2 = -1$$

Simplify the expression by subtracting \frac{1}{784} on both sides

$$-u^2 = -1-\frac{1}{784} = -\frac{785}{784}$$

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

$$u^2 = \frac{785}{784} u = \pm\sqrt{\frac{785}{784}} = \pm \frac{\sqrt{785}}{28}$$

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

$$r =-\frac{1}{28} - \frac{\sqrt{785}}{28} = -1.036 s = -\frac{1}{28} + \frac{\sqrt{785}}{28} = 0.965$$

Evaluate

$$14x^{2}+x-14$$