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.

7a⁴ - 3a⁴ = 4a⁴

The volume of a cylinder is πr²h:

v = πr²h
v = π(1² x 2)
v = 2π

To solve this equation, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

2a(a - x)
2(-9)(-9 + 7)
2(-9)(-2)
(-18)(-2)
36

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 + 6a - 50 = 4a - 2
a² + 6a - 50 + 2 = 4a
a² + 6a - 4a - 48 = 0
a² + 2a - 48 = 0

Next, factor the quadratic equation:

a² + 2a - 48 = 0
(a - 6)(a + 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a - 6) or (a + 8) must equal zero:

If (a - 6) = 0, a must equal 6
If (a + 8) = 0, a must equal -8

So the solution is that a = 6 or -8

A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.