An acute angle measures less than 90°, a right angle measures 90°, and an obtuse angle measures more than 90°.

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.

2a⁹ + 5a⁹ = 7a⁹

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

-8z - 9 = \( \frac{z}{9} \)
9 x (-8z - 9) = z
(9 x -8z) + (9 x -9) = z
-72z - 81 = z
-72z - 81 - z = 0
-72z - z = 81
-73z = 81
z = \( \frac{81}{-73} \)
z = -1\(\frac{8}{73}\)

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 -4 as well and sum (Inside, Outside) to equal 3. For this problem, those two numbers are -1 and 4. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 3y - 4
y² + (-1 + 4)y + (-1 x 4)
(y - 1)(y + 4)

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).