Question

Solve for y by using the quadratic formula: y2 - 4y - 21 = 0.

A. -7, -3
B. 7, 3
C. 7, -3
D. 7, -7

Answer 1

do u know the quadratic formula?

Answer 2

Go to this website and enter the numbers will give you result
http://www.math.com/students/calculators/source/quadratic.htm

Answer 3

The constant on each term is your 'a,b,c' plug them in and you will get two answers that satisfy your equation.
\[\frac{-b \pm \sqrt{b^2-4ac}}{2a}\]