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 2 as well and sum (Inside, Outside) to equal -3. For this problem, those two numbers are -2 and -1. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 3y + 2
y² + (-2 - 1)y + (-2 x -1)
(y - 2)(y - 1)

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

p = x + y + z
p = 15cm + 5cm + 10cm = 30cm

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(5a)(2ab) - (8a²)(2b)
(5 x 2)(a x a x b) - (8 x 2)(a² x b)
(10)(a¹⁺¹ x b) - (16)(a²b)
10a²b - 16a²b
-6a²b

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

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

y² - 3y - 4 = 0
(y + 1)(y - 4) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y + 1) or (y - 4) must equal zero:

If (y + 1) = 0, y must equal -1
If (y - 4) = 0, y must equal 4

So the solution is that y = -1 or 4