Solve x^2+14x+48

$$x ^ { 2 } + 14 x + 48$$

Factor

$$\left(x+6\right)\left(x+8\right)$$

Solution Steps

Factor the expression by grouping. First, the expression needs to be rewritten as x^{2}+ax+bx+48. To find a and b, set up a system to be solved.

$$a+b=14 ab=1\times 48=48$$

Since ab is positive, a and b have the same sign. Since a+b is positive, a and b are both positive. List all such integer pairs that give product 48.

$$1,48 2,24 3,16 4,12 6,8$$

Calculate the sum for each pair.

$$1+48=49 2+24=26 3+16=19 4+12=16 6+8=14$$

The solution is the pair that gives sum 14.

$$a=6 b=8$$

Rewrite x^{2}+14x+48 as \left(x^{2}+6x\right)+\left(8x+48\right).

$$\left(x^{2}+6x\right)+\left(8x+48\right)$$

Factor out x in the first and 8 in the second group.

$$x\left(x+6\right)+8\left(x+6\right)$$

Factor out common term x+6 by using distributive property.

$$\left(x+6\right)\left(x+8\right)$$

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.

$$x^{2}+14x+48=0$$

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.

$$x=\frac{-14±\sqrt{14^{2}-4\times 48}}{2}$$

Square 14.

$$x=\frac{-14±\sqrt{196-4\times 48}}{2}$$

Multiply -4 times 48.

$$x=\frac{-14±\sqrt{196-192}}{2}$$

Add 196 to -192.

$$x=\frac{-14±\sqrt{4}}{2}$$

Take the square root of 4.

$$x=\frac{-14±2}{2}$$

Now solve the equation x=\frac{-14±2}{2} when ± is plus. Add -14 to 2.

$$x=-\frac{12}{2}$$

Divide -12 by 2.

$$x=-6$$

Now solve the equation x=\frac{-14±2}{2} when ± is minus. Subtract 2 from -14.

$$x=-\frac{16}{2}$$

Divide -16 by 2.

$$x=-8$$

Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute -6 for x_{1} and -8 for x_{2}.

$$x^{2}+14x+48=\left(x-\left(-6\right)\right)\left(x-\left(-8\right)\right)$$

Simplify all the expressions of the form p-\left(-q\right) to p+q.

$$x^{2}+14x+48=\left(x+6\right)\left(x+8\right)$$

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.

$$x ^ 2 +14x +48 = 0$$

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

$$r + s = -14 rs = 48$$

Two numbers r and s sum up to -14 exactly when the average of the two numbers is \frac{1}{2}*-14 = -7. 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>

$$r = -7 - u s = -7 + u$$

To solve for unknown quantity u, substitute these in the product equation rs = 48

$$(-7 - u) (-7 + u) = 48$$

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

$$49 - u^2 = 48$$

Simplify the expression by subtracting 49 on both sides

$$-u^2 = 48-49 = -1$$

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

$$u^2 = 1 u = \pm\sqrt{1} = \pm 1$$

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

$$r =-7 - 1 = -8 s = -7 + 1 = -6$$

Evaluate

$$\left(x+6\right)\left(x+8\right)$$