Factor the expression by grouping. First, the expression needs to be rewritten as $10x^{2}+ax+bx-24$. To find $a$ and $b$, set up a system to be solved.
$$a+b=-1$$ $$ab=10\left(-24\right)=-240$$
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 $-240$.
Rewrite $10x^{2}-x-24$ as $\left(10x^{2}-16x\right)+\left(15x-24\right)$.
$$\left(10x^{2}-16x\right)+\left(15x-24\right)$$
Factor out $2x$ in the first and $3$ in the second group.
$$2x\left(5x-8\right)+3\left(5x-8\right)$$
Factor out common term $5x-8$ by using distributive property.
$$\left(5x-8\right)\left(2x+3\right)$$
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 $ax^{2}+bx+c=0$.
$$10x^{2}-x-24=0$$
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.
Now solve the equation $x=\frac{1±31}{20}$ when $±$ is plus. Add $1$ to $31$.
$$x=\frac{32}{20}$$
Reduce the fraction $\frac{32}{20}$ to lowest terms by extracting and canceling out $4$.
$$x=\frac{8}{5}$$
Now solve the equation $x=\frac{1±31}{20}$ when $±$ is minus. Subtract $31$ from $1$.
$$x=-\frac{30}{20}$$
Reduce the fraction $\frac{-30}{20}$ to lowest terms by extracting and canceling out $10$.
$$x=-\frac{3}{2}$$
Factor the original expression using $ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right)$. Substitute $\frac{8}{5}$ for $x_{1}$ and $-\frac{3}{2}$ for $x_{2}$.
Multiply $\frac{5x-8}{5}$ times $\frac{2x+3}{2}$ by multiplying numerator times numerator and denominator times denominator. Then reduce the fraction to lowest terms if possible.
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 $10$
$$x ^ 2 -\frac{1}{10}x -\frac{12}{5} = 0$$
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 $rs = C$
$$r + s = \frac{1}{10} $$ $$ rs = -\frac{12}{5}$$
Two numbers $r$ and $s$ sum up to $\frac{1}{10}$ exactly when the average of the two numbers is $\frac{1}{2}*\frac{1}{10} = \frac{1}{20}$. 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 $u$.
$$r = \frac{1}{20} - u$$ $$s = \frac{1}{20} + u$$
To solve for unknown quantity $u$, substitute these in the product equation $rs = -\frac{12}{5}$
