Solve 149y^2-56y+16

$$149 y ^ { 2 } - 56 y + 16$$

Evaluate

$$149y^{2}-56y+16$$

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 149

$$x ^ 2 -\frac{56}{149}x +\frac{16}{149} = 0$$

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

$$r + s = \frac{56}{149} rs = \frac{16}{149}$$

Two numbers r and s sum up to \frac{56}{149} exactly when the average of the two numbers is \frac{1}{2}*\frac{56}{149} = \frac{28}{149}. 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>

$$r = \frac{28}{149} - u s = \frac{28}{149} + u$$

To solve for unknown quantity u, substitute these in the product equation rs = \frac{16}{149}

$$(\frac{28}{149} - u) (\frac{28}{149} + u) = \frac{16}{149}$$

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

$$\frac{784}{22201} - u^2 = \frac{16}{149}$$

Simplify the expression by subtracting \frac{784}{22201} on both sides

$$-u^2 = \frac{16}{149}-\frac{784}{22201} = \frac{1600}{22201}$$

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

$$u^2 = -\frac{1600}{22201} u = \pm\sqrt{-\frac{1600}{22201}} = \pm \frac{40}{149}i$$

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

$$r =\frac{28}{149} - \frac{40}{149}i = 0.188 - 0.268i s = \frac{28}{149} + \frac{40}{149}i = 0.188 + 0.268i$$

Differentiate w.r.t. y

$$298y-56$$

Steps Using Derivative Rule for Sum

The derivative of a polynomial is the sum of the derivatives of its terms. The derivative of a constant term is 0. The derivative of ax^{n} is nax^{n-1}.

$$2\times 149y^{2-1}-56y^{1-1}$$

Multiply 2 times 149.

$$298y^{2-1}-56y^{1-1}$$

Subtract 1 from 2.

$$298y^{1}-56y^{1-1}$$

Subtract 1 from 1.

$$298y^{1}-56y^{0}$$

For any term t, t^{1}=t.

$$298y-56y^{0}$$

For any term t except 0, t^{0}=1.

$$298y-56$$