The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

x² - 3x - 16 = -x - 1
x² - 3x - 16 + 1 = -x
x² - 3x + x - 15 = 0
x² - 2x - 15 = 0

Next, factor the quadratic equation:

x² - 2x - 15 = 0
(x + 3)(x - 5) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (x + 3) or (x - 5) must equal zero:

If (x + 3) = 0, x must equal -3
If (x - 5) = 0, x must equal 5

So the solution is that x = -3 or 5

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

4a⁷ + 6a⁷ = 10a⁷

A trapezoid is a quadrilateral with one set of parallel sides.

When solving an equation with two variables, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

A rectangle is a parallelogram containing four right angles. Opposite sides (a = c, b = d) are equal and the perimeter is the sum of the lengths of all sides (a + b + c + d) or, comonly, 2 x length x width. The area of a rectangle is length x width. A square is a rectangle with four equal length sides. The perimeter of a square is 4 x length of one side (4s) and the area is the length of one side squared (s²).