Solve 9z^2+95z+10

$$9 z ^ { 2 } + 95 z + 10$$

Factor

$$9\left(z-\frac{-\sqrt{8665}-95}{18}\right)\left(z-\frac{\sqrt{8665}-95}{18}\right)$$

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.

$$9z^{2}+95z+10=0$$

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.

$$z=\frac{-95±\sqrt{95^{2}-4\times 9\times 10}}{2\times 9}$$

Square 95.

$$z=\frac{-95±\sqrt{9025-4\times 9\times 10}}{2\times 9}$$

Multiply -4 times 9.

$$z=\frac{-95±\sqrt{9025-36\times 10}}{2\times 9}$$

Multiply -36 times 10.

$$z=\frac{-95±\sqrt{9025-360}}{2\times 9}$$

Add 9025 to -360.

$$z=\frac{-95±\sqrt{8665}}{2\times 9}$$

Multiply 2 times 9.

$$z=\frac{-95±\sqrt{8665}}{18}$$

Now solve the equation z=\frac{-95±\sqrt{8665}}{18} when ± is plus. Add -95 to \sqrt{8665}.

$$z=\frac{\sqrt{8665}-95}{18}$$

Now solve the equation z=\frac{-95±\sqrt{8665}}{18} when ± is minus. Subtract \sqrt{8665} from -95.

$$z=\frac{-\sqrt{8665}-95}{18}$$

Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute \frac{-95+\sqrt{8665}}{18} for x_{1} and \frac{-95-\sqrt{8665}}{18} for x_{2}.

$$9z^{2}+95z+10=9\left(z-\frac{\sqrt{8665}-95}{18}\right)\left(z-\frac{-\sqrt{8665}-95}{18}\right)$$

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 9

$$x ^ 2 +\frac{95}{9}x +\frac{10}{9} = 0$$

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

$$r + s = -\frac{95}{9} rs = \frac{10}{9}$$

Two numbers r and s sum up to -\frac{95}{9} exactly when the average of the two numbers is \frac{1}{2}*-\frac{95}{9} = -\frac{95}{18}. 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>

$$r = -\frac{95}{18} - u s = -\frac{95}{18} + u$$

To solve for unknown quantity u, substitute these in the product equation rs = \frac{10}{9}

$$(-\frac{95}{18} - u) (-\frac{95}{18} + u) = \frac{10}{9}$$

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

$$\frac{9025}{324} - u^2 = \frac{10}{9}$$

Simplify the expression by subtracting \frac{9025}{324} on both sides

$$-u^2 = \frac{10}{9}-\frac{9025}{324} = -\frac{8665}{324}$$

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

$$u^2 = \frac{8665}{324} u = \pm\sqrt{\frac{8665}{324}} = \pm \frac{\sqrt{8665}}{18}$$

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

$$r =-\frac{95}{18} - \frac{\sqrt{8665}}{18} = -10.449 s = -\frac{95}{18} + \frac{\sqrt{8665}}{18} = -0.106$$

Evaluate

$$9z^{2}+95z+10$$