An acute angle measures less than 90°, a right angle measures 90°, and an obtuse angle measures more than 90°.

To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses:

(y + 7)(y + 7)
(y x y) + (y x 7) + (7 x y) + (7 x 7)
y² + 7y + 7y + 49
y² + 14y + 49

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.

3a - 5a = -2a

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

-9c - 3 = \( \frac{c}{-4} \)
-4 x (-9c - 3) = c
(-4 x -9c) + (-4 x -3) = c
36c + 12 = c
36c + 12 - c = 0
36c - c = -12
35c = -12
c = \( \frac{-12}{35} \)
c = -\(\frac{12}{35}\)

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.