Question

Can someone explain this to me?
Solve the equation by completing the square: 2x2 - 20x = 8

Answer 1

add 8 both sides and use quadratic formula

Answer 2

and you get 2x^2-20x-8=0 ??? or no?

Answer 3

yes

Answer 4

and then what?

Answer 5

2x2 - 20x - 8 = 0
2 ( x2 -10x - 4 ) = 0
2 ( (x-5)^2 - 4 - 5 = 0
2 ( (x-5)^2 - 9 ) = 0
2(x-5)^2- 4.5 = 0

Answer 6

you can use the quadratic formula

Answer 7

or try to factor first

Answer 8

i factor -8?

Answer 9

did you understand what i did to complete the square ?

Answer 10

not really >.< this really confuses me.

Answer 11

im terrible at math

Answer 12

http://www.webgraphing.com/quadraticequation_completingthesquare.jsp
here is your problem

Answer 13

ok you have 2x^2 - 20x -8 = 0
you cant complete the square when there is a 2 in front of the x^2
so: you remove the 2 outside of the eq. = 2 [ (x^2 -10 x -4 ) = 0
Notice i divide the 20x by 2 and 8 by 2 also...
then : 2 [ (x-5)^2 - 4 -5 ) ] Here i divide the 10 by 2 so that I obtain it in a form ( a + b )^2
and I subtract it from the -4
then you will hve 2 [ ( x-5)^2 -9 ] = 0
then you multiply the whole by 2 : 2(x-5)^2- 9/2 = 0
9/2 = 4.5 :) hope I help...

Answer 14

Thank you, guys :D
I appreciate it! (: