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° - 43° - 23° = 114°

So, d° = 23° + 114° = 137°

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° - 43° = 137°

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).

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 -5 as well and sum (Inside, Outside) to equal -4. For this problem, those two numbers are -5 and 1. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 4y - 5
y² + (-5 + 1)y + (-5 x 1)
(y - 5)(y + 1)

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.

3a + 7a = 10a

A trapezoid is a quadrilateral with one set of parallel sides.