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

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 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.

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.

5a⁷ - 2a⁷ = 3a⁷

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:

y² + 17y + 45 = 4y + 3
y² + 17y + 45 - 3 = 4y
y² + 17y - 4y + 42 = 0
y² + 13y + 42 = 0

Next, factor the quadratic equation:

y² + 13y + 42 = 0
(y + 6)(y + 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y + 6) or (y + 7) must equal zero:

If (y + 6) = 0, y must equal -6
If (y + 7) = 0, y must equal -7

So the solution is that y = -6 or -7