Question

Solve 3x2 - 12x + 2 = 0 by using a method different from the one you used in Part B. Show the steps of your work.

Answer 1

Please help! For part B i have:

Answer 2

2x^2 - 9x + 7 = 0
(-b +/- √(b^2 - 4ac)) / 2a
Where:
a = 2
b = 9
c = -7
(-9 +/-sqrt( 9^2 - 4(2)(-7)))/2(2)
(-9 +/- sqrt(81 + 56))/4
(-9 +/- sqrt137)/4
x = (-9 + 11.7)/4
x = 2.7/4
x =0.675

Answer 3

What other options do you have now, do you have ideas?

Answer 4

3x^@ - 12x = 0
3x^2 = 12x
x^2 = 4x
x = 4
This is what i have...is it right?

Answer 5

Well it is almost correct. When you divide both sides by x, though, you are making an assumption that x is not equal to 0.
However, what happens when you have x=0 in your original equation?

Answer 6

12x + 0 = 12x so i thought thats how to do it.

Answer 7

3x^2 - 12 x = 0 at x=0
3*(0)^2 - 12 * 0 = 0
0 = 0 That is also a solution. :)

Answer 8

So that means they are both right?

Answer 9

Yes. Because you divided both sides by x, which is not allowed when x=0 (division by zero is bad), you removed that information from the equation essentially. So you'd have to test it out afterwards to make sure!

A more standard method that takes advantage of the like-factor of x, is by factoring though.
3x^2 - 12x = 0
We could just pull out an x:
x (3x - 12) = 0
and use zero-product property.
x=0 or 3x - 12 = 0 This will get the same values, without needing to test. :)

Answer 10

Thank you good sir!

Answer 11

You're welcome! :)