The formula for circumference is circle diameter x π. Circle diameter is 2 x radius:

c = πd
c = π(2 * r)
c = π(2 * 3)
c = 6π

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.

8a + 2a = 10a

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:

y² - 11y - 4 = -4y + 4
y² - 11y - 4 - 4 = -4y
y² - 11y + 4y - 8 = 0
y² - 7y - 8 = 0

Next, factor the quadratic equation:

y² - 7y - 8 = 0
(y + 1)(y - 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y + 1) or (y - 8) must equal zero:

If (y + 1) = 0, y must equal -1
If (y - 8) = 0, y must equal 8

So the solution is that y = -1 or 8

The coordinate grid is composed of a horizontal x-axis and a vertical y-axis. The center of the grid, where the x-axis and y-axis meet, is called the origin.

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 < sign and the answer on the other.

-9a - 3 < \( \frac{a}{2} \)
2 x (-9a - 3) < a
(2 x -9a) + (2 x -3) < a
-18a - 6 < a
-18a - 6 - a < 0
-18a - a < 6
-19a < 6
a < \( \frac{6}{-19} \)
a < -\(\frac{6}{19}\)