Solving Quadratic Equation (By Factoring)

[element]

Hey,

Could someone show me step-by-step on how to solve the quadratic equation: 2x²-7x-30=0 by factoring. I have quite a bit of trouble on understanding how to factor, so please explain as simply as you can.

Thank you!

-Mark

 

[arthur ohlsten]

2x^2-7x-30=0

factors of 2 = 1,2
factors of 30 = 1,30 2,15 3,10 5,6

we want a ste whose difference (last term is -) of cross products =7
1,2 1,30 no good crossproduct = 28 or 59
1,2 2,15 no good cross product either = 11 or 28
1,2 3,10 no good cross product either =14 or 17
1,2 5,6 good difference of cross products either 4 or 7
we want 7 6times2 - 1times5 = 7
(1x-6) ( 2x+5)=0
Best I can do
Arthur

 

[element]

2x^2-7x-30=0

factors of 2 = 1,2
factors of 30 = 1,30 2,15 3,10 5,6

we want a ste whose difference (last term is -) of cross products =7
1,2 1,30 no good crossproduct = 28 or 59
1,2 2,15 no good cross product either = 11 or 28
1,2 3,10 no good cross product either =14 or 17
1,2 5,6 good difference of cross products either 4 or 7
we want 7 6times2 - 1times5 = 7
(1x-6) ( 2x+5)=0
Best I can do
Arthur

Ok well thats factored but what would it be solved?(completely)

 

[Gene]

Once you have it factored you just set each factor = 0
x-6=0
2x+5=0
to get the two values of x that work.

BTW it isn't necessary to copy everything from a previous post. It's only a click away.

 

[element]

Can someone try doing it again. Arthur, don't think that was the right answer the back of the book says: x=-5/2 or x=6

 

[tkhunny]

Can someone try doing it again. Arthur, don't think that was the right answer the back of the book says: x=-5/2 or x=6

Those are the answers you have been given here.

You have the factors.

(1x-6) ( 2x+5)=0

You have been instructed what to do with them.

x-6=0
2x+5=0

Now do it.