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 + 9)(y - 7)
(y x y) + (y x -7) + (9 x y) + (9 x -7)
y² - 7y + 9y - 63
y² + 2y - 63

The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 8 x 9 = \( \frac{72}{2} \) = 36

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

a² - 3a - 28 = 0
(a + 4)(a - 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a + 4) or (a - 7) must equal zero:

If (a + 4) = 0, a must equal -4
If (a - 7) = 0, a must equal 7

So the solution is that a = -4 or 7

The area of a parallelogram is equal to its length x width:

a = l x w
a = a x b
a = 1 x 2
a = 2

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.