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.

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).

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:

z² - 15z + 13 = -4z - 5
z² - 15z + 13 + 5 = -4z
z² - 15z + 4z + 18 = 0
z² - 11z + 18 = 0

Next, factor the quadratic equation:

z² - 11z + 18 = 0
(z - 2)(z - 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 2) or (z - 9) must equal zero:

If (z - 2) = 0, z must equal 2
If (z - 9) = 0, z must equal 9

So the solution is that z = 2 or 9

A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

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 > sign and the answer on the other.

a + 6 > -3 - 9a
a > -3 - 9a - 6
a + 9a > -3 - 6
10a > -9
a > \( \frac{-9}{10} \)
a > -\(\frac{9}{10}\)