SOLUTION: Solve the following quadratic equations: 1. (2x + 3)(5x – 15) = 0 2. x2 – 8 =0 3. x2 + 5x – 36 = 0 4. x2 = -8x + 15

Algebra ->  Equations -> SOLUTION: Solve the following quadratic equations: 1. (2x + 3)(5x – 15) = 0 2. x2 – 8 =0 3. x2 + 5x – 36 = 0 4. x2 = -8x + 15       Log On


   

Question 1120356: Solve the following quadratic equations:
1. (2x + 3)(5x – 15) = 0
2. x2 – 8 =0
3. x2 + 5x – 36 = 0
4. x2 = -8x + 15
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Only doing #4:

x%5E2%2B8x-15=0
-
discriminant 8%5E2-4%2A1%2A%28-15%29=64%2B60=124=31%2A2%5E2


x=%28-8%2B-+2%2Asqrt%2831%29%29%2F2

highlight%28x=-4%2B-+sqrt%2831%29%29

Answer by ikleyn(52778) About Me  (Show Source):
You can put this solution on YOUR website!
.
Solving quadratic equations is one of the basic skills each student must develop studying Algebra.

To help you to develop such skills,  the group of lessons was created in this site.  They are free of charge for you.
Listed below are only introductory  (basic)  lessons of this series:

    - Introduction into Quadratic Equations
    - PROOF of quadratic formula by completing the square
    - HOW TO complete the square - Learning by examples
    - HOW TO solve quadratic equation by completing the square - Learning by examples
    - Solving quadratic equations without quadratic formula