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 56 as well and sum (Inside, Outside) to equal 15. For this problem, those two numbers are 7 and 8. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 15y + 56
y² + (7 + 8)y + (7 x 8)
(y + 7)(y + 8)

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 6 + 4 + 9 + 1
p = 20

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 + 2)
(y x y) + (y x 2) + (9 x y) + (9 x 2)
y² + 2y + 9y + 18
y² + 11y + 18

An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 23° - 68° = 89°

So, d° = 68° + 89° = 157°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 23° = 157°