Question 28020: 3x=x+12
Answer by sdmmadam@yahoo.com(530)   (Show Source):
You can put this solution on YOUR website! 3x=x+12
This is not quadratic. This is linear in x.
(3x-x) = 12 (bringing x from the right to the left, change side then change sign, in other words add - x to both the sides.
2x = 12
x = 12/2 = 6
But if it has to be quadratic then it might be
3x^2= 5x+12
Putting it in the stand ard form
3x^2-5x -12 = 0----(1)
3x^2+(-9x+4x)-12 = 0
(splitting the middle term as the sum of two terms in such a way that these two when multiplied(of course along with the signs)should give the product of the square term and the constant term.)
[That is [-5x =(-9)x+(4)x and (-9x)X(4x) = -36x^2= (3x^2)X(-12)]
(3x^2-9x)+(4x-12)=0 (by additive associativity)
3x(x-3)+4(x-3) = 0
3xp+4p = 0 where p = (x-3)
p(3x+4) = 0
That is (x-3)(3x+4) = 0
(x-3) = 0 gives x= 3 and (3x+4) = 0 gives x = -4/3
Answer: x= 3 and x = -4/3
Verification: Putting x=3 in (1), we getLHs=27-15-12=0=RHs
x=-4/3 in (1) gives LHS = 16/3+20/3-12 = 0 = RHS
Our values for x are correct
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