An isosceles triangle has two sides of equal length. An equilateral triangle has three sides of equal length. In a right triangle, two sides meet at a right angle.

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 42° - 55° = 83°

A line on the coordinate grid can be defined by a slope-intercept equation: y = mx + b. For a given value of x, the value of y can be determined given the slope (m) and y-intercept (b) of the line. The slope of a line is change in y over change in x, \({\Delta y \over \Delta x}\), and the y-intercept is the y-coordinate where the line crosses the vertical y-axis.

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:

a² - 13a - 6 = -5a + 3
a² - 13a - 6 - 3 = -5a
a² - 13a + 5a - 9 = 0
a² - 8a - 9 = 0

Next, factor the quadratic equation:

a² - 8a - 9 = 0
(a + 1)(a - 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a + 1) or (a - 9) must equal zero:

If (a + 1) = 0, a must equal -1
If (a - 9) = 0, a must equal 9

So the solution is that a = -1 or 9

A monomial contains one term, a binomial contains two terms, and a polynomial contains more than two terms.