Factor
\left(x-16\right)\left(x+6\right)
Evaluate
\left(x-16\right)\left(x+6\right)
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a+b=-10 ab=1\left(-96\right)=-96
Factor the expression by grouping. First, the expression needs to be rewritten as x^{2}+ax+bx-96. To find a and b, set up a system to be solved.
1,-96 2,-48 3,-32 4,-24 6,-16 8,-12
Since ab is negative, a and b have the opposite signs. Since a+b is negative, the negative number has greater absolute value than the positive. List all such integer pairs that give product -96.
1-96=-95 2-48=-46 3-32=-29 4-24=-20 6-16=-10 8-12=-4
Calculate the sum for each pair.
a=-16 b=6
The solution is the pair that gives sum -10.
\left(x^{2}-16x\right)+\left(6x-96\right)
Rewrite x^{2}-10x-96 as \left(x^{2}-16x\right)+\left(6x-96\right).
x\left(x-16\right)+6\left(x-16\right)
Factor out x in the first and 6 in the second group.
\left(x-16\right)\left(x+6\right)
Factor out common term x-16 by using distributive property.
x^{2}-10x-96=0
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.
x=\frac{-\left(-10\right)±\sqrt{\left(-10\right)^{2}-4\left(-96\right)}}{2}
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(-10\right)±\sqrt{100-4\left(-96\right)}}{2}
Square -10.
x=\frac{-\left(-10\right)±\sqrt{100+384}}{2}
Multiply -4 times -96.
x=\frac{-\left(-10\right)±\sqrt{484}}{2}
Add 100 to 384.
x=\frac{-\left(-10\right)±22}{2}
Take the square root of 484.
x=\frac{10±22}{2}
The opposite of -10 is 10.
x=\frac{32}{2}
Now solve the equation x=\frac{10±22}{2} when ± is plus. Add 10 to 22.
x=16
Divide 32 by 2.
x=-\frac{12}{2}
Now solve the equation x=\frac{10±22}{2} when ± is minus. Subtract 22 from 10.
x=-6
Divide -12 by 2.
x^{2}-10x-96=\left(x-16\right)\left(x-\left(-6\right)\right)
Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute 16 for x_{1} and -6 for x_{2}.
x^{2}-10x-96=\left(x-16\right)\left(x+6\right)
Simplify all the expressions of the form p-\left(-q\right) to p+q.
x ^ 2 -10x -96 = 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 = 10 rs = -96
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 = 5 - u s = 5 + u
Two numbers r and s sum up to 10 exactly when the average of the two numbers is \frac{1}{2}*10 = 5. 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>
(5 - u) (5 + u) = -96
To solve for unknown quantity u, substitute these in the product equation rs = -96
25 - u^2 = -96
Simplify by expanding (a -b) (a + b) = a^2 – b^2
-u^2 = -96-25 = -121
Simplify the expression by subtracting 25 on both sides
u^2 = 121 u = \pm\sqrt{121} = \pm 11
Simplify the expression by multiplying -1 on both sides and take the square root to obtain the value of unknown variable u
r =5 - 11 = -6 s = 5 + 11 = 16
The factors r and s are the solutions to the quadratic equation. Substitute the value of u to compute the r and s.
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