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.

5a - 9a = -4a

To find the diagonal we need to know the length of one of the square's sides. We know the area and the area of a square is the length of one side squared:

a = s²

so the length of one side of the square is:

s = \( \sqrt{a} \) = \( \sqrt{36} \) = 6

The Pythagorean theorem defines the square of the hypotenuse (diagonal) of a triangle with a right angle as the sum of the squares of the other two sides:

c² = a² + b²
c² = 6² + 6²
c² = 72
c = \( \sqrt{72} \) = \( \sqrt{36 x 2} \) = \( \sqrt{36} \) \( \sqrt{2} \)
c = 6\( \sqrt{2} \)

The area of a rectangle is equal to its length x width:

a = l x w
a = a x b
a = 7 x 2
a = 14

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

y² - 15y + 54 = 0
(y - 6)(y - 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y - 6) or (y - 9) must equal zero:

If (y - 6) = 0, y must equal 6
If (y - 9) = 0, y must equal 9

So the solution is that y = 6 or 9

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