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.

4a - 4a = 0a

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

c² - 9c + 18 = 0
(c - 3)(c - 6) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (c - 3) or (c - 6) must equal zero:

If (c - 3) = 0, c must equal 3
If (c - 6) = 0, c must equal 6

So the solution is that c = 3 or 6

A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.

The entire length of this line is represented by AD which is AB + BD:

AD = AB + BD

To solve this equation, isolate the variable for which you are solving (c) on one side of the equation and put everything else on the other side.

-4c - 4x = -6c - x - 3
-4c = -6c - x - 3 + 4x
-4c + 6c = -x - 3 + 4x
2c = 3x - 3
c = \( \frac{3x - 3}{2} \)
c = \( \frac{3x}{2} \) + \( \frac{-3}{2} \)
c = 1\(\frac{1}{2}\)x - 1\(\frac{1}{2}\)