To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

4a x 7b = (4 x 7) (a x b) = 28ab

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

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

a = l x w
a = a x b
a = 8 x 4
a = 32

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 -45 as well and sum (Inside, Outside) to equal -4. For this problem, those two numbers are -9 and 5. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 4y - 45
y² + (-9 + 5)y + (-9 x 5)
(y - 9)(y + 5)