A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.

According to the Pythagorean theorem, the hypotenuse squared is equal to the sum of the two perpendicular sides squared:

c² = a² + b²
c² = 8² + 6²
c² = 64 + 36
c² = 100
c = \( \sqrt{100} \)
c = 10

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.

9a⁶ + 9a⁶ = 18a⁶

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 5. 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 + 5y + 4
y² + (1 + 4)y + (1 x 4)
(y + 1)(y + 4)

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.

4a - 9 = 1 + 5a
4a = 1 + 5a + 9
4a - 5a = 1 + 9
-a = 10
a = \( \frac{10}{-1} \)
a = -10