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.

8a⁹ + 7a⁹ = 15a⁹

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(6 + 2)(4)
a = ½(8)(4)
a = ½(32) = \( \frac{32}{2} \)
a = 16

A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

To factor a quadratic expression, apply the FOIL method (First, Outside, Inside, Last) in reverse. First, find the two Last terms that will multiply to produce 12 as well and sum (Inside, Outside) to equal -7. For this problem, those two numbers are -4 and -3. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 7y + 12
y² + (-4 - 3)y + (-4 x -3)
(y - 4)(y - 3)