The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

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.

To factor a quadratic expression, apply the FOIL method (First, Outside, Inside, Last) in reverse. First, find the two Last terms that will multiply to produce -72 as well and sum (Inside, Outside) to equal -1. For this problem, those two numbers are -9 and 8. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - y - 72
y² + (-9 + 8)y + (-9 x 8)
(y - 9)(y + 8)

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

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:

b² + 12b + 22 = 3b + 4
b² + 12b + 22 - 4 = 3b
b² + 12b - 3b + 18 = 0
b² + 9b + 18 = 0

Next, factor the quadratic equation:

b² + 9b + 18 = 0
(b + 3)(b + 6) = 0

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

If (b + 3) = 0, b must equal -3
If (b + 6) = 0, b must equal -6

So the solution is that b = -3 or -6