The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 8 x 8) + (2 x 8 x 4) + (2 x 8 x 4)
sa = (128) + (64) + (64)
sa = 256

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:

x² - 4x - 30 = -4x - 5
x² - 4x - 30 + 5 = -4x
x² - 4x + 4x - 25 = 0
x² - 25 = 0

Next, factor the quadratic equation:

x² - 25 = 0
(x - 5)(x + 5) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (x - 5) or (x + 5) must equal zero:

If (x - 5) = 0, x must equal 5
If (x + 5) = 0, x must equal -5

So the solution is that x = 5 or -5

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.

2a³ + 5a³ = 7a³

The slope-intercept equation for a line is y = mx + b where m is the slope and b is the y-intercept of the line. From the graph, you can see that the y-intercept (the y-value from the point where the line crosses the y-axis) is -3. The slope of this line is the change in y divided by the change in x. The endpoints of this line segment are at (-2, 1) and (2, -7) so the slope becomes:

Plugging these values into the slope-intercept equation:

y = -2x - 3

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 12cm + 10cm + 9cm = 31cm