need help solving equation

[milanna]

3x(x -1) = 7x^2 - 4x

I get the answer {0, 4}, but I think I am wrong.

 

[stapel]

To check the solution to any "solving" exercise, plug your answers back into the original problem. So:

. . . . .x = 0:

. . . . .3[0]([0] - 1) ?=? 7[0]² - 4[0]
. . . . .0(0 - 1) ?=? 0 - 0
. . . . .0 ?=? 0

This solution checks. (Good job!) Now see if the other solution "checks" as well.

Eliz.

 

[milanna]

after I plug in the other number (4) I ended up with

12(3) = 28^2 - 16
36 = 768

so the solution is just 0 then?

 

[Denis]

Try solving again...CAREFULLY...you will not get 4 as solution;
you will get a fraction instead

 

[milanna]

ok I redid it and this time I came up with {0, -1/4}

 

[Denis]

very close...try again, until you get +1/4 :evil:

 

[milanna]

Thank you, I'm very bad at math. But trying, and slowly getting better.

 

[Denis]

Don't let stuff like (x - 6)(x + 9) = 0 throw you off;
you really have 2 simple equations:
x - 6 = 0 : so x = 6
x + 9 = 0 : so x = -9