Question

Solve by completing the square:

9x^2+30x+0=0 and 4x^2-6x=0

Answer 1

FOR 9x^2+30x+0=0:
- divide the middle term 30x by (2*3x) and then square the result. you should get 25
- Add 25 to both sides
(3x + 5)^2 = 25
3x + 5 = +/- 5
Then solve for x

Answer 2

Use same technique for the other one

Answer 3

Where did (2*3x) come from and how did it get 25?

Answer 4

so the formula for (a + b)^2 = a^2 + 2ab + b^2
when you use completing the square, you are finding b^2 and what you have is a^2 + 2ab
so to find b, u need to divide 2ab by 2a, and then you square the result to get b^2
to find "a", you just take the principal square root of a^2 (first term)
IN THIS CASE
30x/2*3x = 30x/6x = 5 = b
5^2 = 25 = b^2

Answer 5

square root of 9x^2 = 3x