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.

5a + 9a = 14a

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(6²) + 2π(6 x 1)
sa = 2π(36) + 2π(6)
sa = (2 x 36)π + (2 x 6)π
sa = 72π + 12π
sa = 84π

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

x² - x - 12 = 0
(x + 3)(x - 4) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (x + 3) or (x - 4) must equal zero:

If (x + 3) = 0, x must equal -3
If (x - 4) = 0, x must equal 4

So the solution is that x = -3 or 4

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.

6a⁹ - 4a⁹ = 2a⁹

A line on the coordinate grid can be defined by a slope-intercept equation: y = mx + b. For a given value of x, the value of y can be determined given the slope (m) and y-intercept (b) of the line. The slope of a line is change in y over change in x, \({\Delta y \over \Delta x}\), and the y-intercept is the y-coordinate where the line crosses the vertical y-axis.