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Differentiate w.r.t. x
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x ^ 2 +16x +65 = 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 = -16 rs = 65
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 = -8 - u s = -8 + u
Two numbers r and s sum up to -16 exactly when the average of the two numbers is \frac{1}{2}*-16 = -8. 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>
(-8 - u) (-8 + u) = 65
To solve for unknown quantity u, substitute these in the product equation rs = 65
64 - u^2 = 65
Simplify by expanding (a -b) (a + b) = a^2 – b^2
-u^2 = 65-64 = 1
Simplify the expression by subtracting 64 on both sides
u^2 = -1 u = \pm\sqrt{-1} = \pm i
Simplify the expression by multiplying -1 on both sides and take the square root to obtain the value of unknown variable u
r =-8 - i s = -8 + i
The factors r and s are the solutions to the quadratic equation. Substitute the value of u to compute the r and s.
2x^{2-1}+16x^{1-1}
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}.
2x^{1}+16x^{1-1}
Subtract 1 from 2.
2x^{1}+16x^{0}
Subtract 1 from 1.
2x+16x^{0}
For any term t, t^{1}=t.
2x+16\times 1
For any term t except 0, t^{0}=1.
2x+16
For any term t, t\times 1=t and 1t=t.