Solve 16x^2+8x+1

$$16 x ^ { 2 } + 8 x + 1$$

Factor

$$\left(4x+1\right)^{2}$$

Solution Steps

Factor the expression by grouping. First, the expression needs to be rewritten as 16x^{2}+ax+bx+1. To find a and b, set up a system to be solved.

$$a+b=8 ab=16\times 1=16$$

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 16.

$$1,16 2,8 4,4$$

Calculate the sum for each pair.

$$1+16=17 2+8=10 4+4=8$$

The solution is the pair that gives sum 8.

$$a=4 b=4$$

Rewrite 16x^{2}+8x+1 as \left(16x^{2}+4x\right)+\left(4x+1\right).

$$\left(16x^{2}+4x\right)+\left(4x+1\right)$$

Factor out 4x in 16x^{2}+4x.

$$4x\left(4x+1\right)+4x+1$$

Factor out common term 4x+1 by using distributive property.

$$\left(4x+1\right)\left(4x+1\right)$$

Rewrite as a binomial square.

$$\left(4x+1\right)^{2}$$

Steps Using Square Of Binomial

This trinomial has the form of a trinomial square, perhaps multiplied by a common factor. Trinomial squares can be factored by finding the square roots of the leading and trailing terms.

$$factor(16x^{2}+8x+1)$$

Find the greatest common factor of the coefficients.

$$gcf(16,8,1)=1$$

Find the square root of the leading term, 16x^{2}.

$$\sqrt{16x^{2}}=4x$$

The trinomial square is the square of the binomial that is the sum or difference of the square roots of the leading and trailing terms, with the sign determined by the sign of the middle term of the trinomial square.

$$\left(4x+1\right)^{2}$$

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.

$$16x^{2}+8x+1=0$$

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.

$$x=\frac{-8±\sqrt{8^{2}-4\times 16}}{2\times 16}$$

Square 8.

$$x=\frac{-8±\sqrt{64-4\times 16}}{2\times 16}$$

Multiply -4 times 16.

$$x=\frac{-8±\sqrt{64-64}}{2\times 16}$$

Add 64 to -64.

$$x=\frac{-8±\sqrt{0}}{2\times 16}$$

Take the square root of 0.

$$x=\frac{-8±0}{2\times 16}$$

Multiply 2 times 16.

$$x=\frac{-8±0}{32}$$

Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute -\frac{1}{4} for x_{1} and -\frac{1}{4} for x_{2}.

$$16x^{2}+8x+1=16\left(x-\left(-\frac{1}{4}\right)\right)\left(x-\left(-\frac{1}{4}\right)\right)$$

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

$$16x^{2}+8x+1=16\left(x+\frac{1}{4}\right)\left(x+\frac{1}{4}\right)$$

Add \frac{1}{4} to x by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$16x^{2}+8x+1=16\times \frac{4x+1}{4}\left(x+\frac{1}{4}\right)$$

Add \frac{1}{4} to x by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$16x^{2}+8x+1=16\times \frac{4x+1}{4}\times \frac{4x+1}{4}$$

Multiply \frac{4x+1}{4} times \frac{4x+1}{4} by multiplying numerator times numerator and denominator times denominator. Then reduce the fraction to lowest terms if possible.

$$16x^{2}+8x+1=16\times \frac{\left(4x+1\right)\left(4x+1\right)}{4\times 4}$$

Multiply 4 times 4.

$$16x^{2}+8x+1=16\times \frac{\left(4x+1\right)\left(4x+1\right)}{16}$$

Cancel out 16, the greatest common factor in 16 and 16.

$$16x^{2}+8x+1=\left(4x+1\right)\left(4x+1\right)$$

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.This is achieved by dividing both sides of the equation by 16

$$x ^ 2 +\frac{1}{2}x +\frac{1}{16} = 0$$

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

$$r + s = -\frac{1}{2} rs = \frac{1}{16}$$

Two numbers r and s sum up to -\frac{1}{2} exactly when the average of the two numbers is \frac{1}{2}*-\frac{1}{2} = -\frac{1}{4}. 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>

$$r = -\frac{1}{4} - u s = -\frac{1}{4} + u$$

To solve for unknown quantity u, substitute these in the product equation rs = \frac{1}{16}

$$(-\frac{1}{4} - u) (-\frac{1}{4} + u) = \frac{1}{16}$$

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

$$\frac{1}{16} - u^2 = \frac{1}{16}$$

Simplify the expression by subtracting \frac{1}{16} on both sides

$$-u^2 = \frac{1}{16}-\frac{1}{16} = 0$$

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

$$u^2 = 0 u = 0$$

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

$$r = s = -\frac{1}{4} = -0.250$$

Evaluate

$$\left(4x+1\right)^{2}$$