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.

9a - 8a = 1a

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:

c² - 15c + 25 = -3c - 2
c² - 15c + 25 + 2 = -3c
c² - 15c + 3c + 27 = 0
c² - 12c + 27 = 0

Next, factor the quadratic equation:

c² - 12c + 27 = 0
(c - 3)(c - 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (c - 3) or (c - 9) must equal zero:

If (c - 3) = 0, c must equal 3
If (c - 9) = 0, c must equal 9

So the solution is that c = 3 or 9

The Pythagorean theorem defines the relationship between the side lengths of a right triangle. The length of the hypotenuse squared (c²) is equal to the sum of the two perpendicular sides squared (a² + b²): c² = a² + b² or, solved for c, \(c = \sqrt{a + b}\)

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 - 3)(y + 1)
(y x y) + (y x 1) + (-3 x y) + (-3 x 1)
y² + y - 3y - 3
y² - 2y - 3

You can only add or subtract monomials that have the same variable and the same exponent. For example, 2a + 4a = 6a and 4a² - a² = 3a² but 2a + 4b and 7a - 3b cannot be combined. However, you can multiply and divide monomials with unlike terms. For example, 2a x 6b = 12ab.