SOLUTION: 3(5+3x)-(x-3)=0 15+9x-x+3=0 18+8x=0 8x=-18 x=-9/4=2.25 If the above is correct, if I put x back into the original equation: 3(5+(3x2.25))-(2.25-3)=0 3(5+6.75)-(-0.75)=0 3

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: 3(5+3x)-(x-3)=0 15+9x-x+3=0 18+8x=0 8x=-18 x=-9/4=2.25 If the above is correct, if I put x back into the original equation: 3(5+(3x2.25))-(2.25-3)=0 3(5+6.75)-(-0.75)=0 3      Log On


   

Question 681503: 3(5+3x)-(x-3)=0
15+9x-x+3=0
18+8x=0
8x=-18
x=-9/4=2.25
If the above is correct, if I put x back into the original equation:
3(5+(3x2.25))-(2.25-3)=0
3(5+6.75)-(-0.75)=0
3x11.75+0.75=0
35.25+0.75=0
36=0!!
That seems nonsensical. I would be very grateful for an explanation and solution to this problem.
Answer by MathTherapy(10551) About Me  (Show Source):
You can put this solution on YOUR website!
3(5+3x)-(x-3)=0
15+9x-x+3=0
18+8x=0
8x=-18
x=-9/4=2.25
If the above is correct, if I put x back into the original equation:
3(5+(3x2.25))-(2.25-3)=0
3(5+6.75)-(-0.75)=0
3x11.75+0.75=0
35.25+0.75=0
36=0!!
That seems nonsensical. I would be very grateful for an explanation and solution to this problem.

Your method is 100% CORRECT, up until the final calculation when you divided - 9 by 4, which should have given you an x value of highlight_green%28-+2.25%29, not 2.25.

Just try to be more careful in the future, especially with THOSE SIGNS, and try to go over your work whenever something doesn't seem right. As you have seen, not including the sign in your final calculation for the variable resulted in a solution that DIDN'T MAKE SENSE.