SOLUTION: 3-(5x-4)-9x=21 I don't know what to do! I tried to solve this way: -5x-9x=21-3+4 -14x=22 x= -22/14 but this isn't right... please help

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: 3-(5x-4)-9x=21 I don't know what to do! I tried to solve this way: -5x-9x=21-3+4 -14x=22 x= -22/14 but this isn't right... please help      Log On


   

Question 738487: 3-(5x-4)-9x=21
I don't know what to do! I tried to solve this way:
-5x-9x=21-3+4
-14x=22
x= -22/14
but this isn't right...
please help
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+3-%285x-4%29-9x=21+
+3+-+5x+%2B+4+-+9x+=+21+
+-5x+-+9x+=+-3+-4+%2B+21+
Multiply both sides by +-1+
+5x+%2B+9x+=+3+%2B+4+-+21+
+14x+=+-14+
+x+=+-1+
-----------
Your problem was dealing with +-%28+5x+-+4+%29+
Remember that (-) x (-) = (+), so
+-%285x+-+4+%29+=+-5x+%2B+4+
-----------
Check the answer:
+3-%285x-4%29-9x=21+
+3-%285%2A%28-1%29-4%29-9%2A%28-1%29+=+21+
+3+-+%28+-5+-+4+%29+%2B+9+=+21+
+3+-%28-9+%29+%2B+9+=+21+
+3+%2B+9+%2B+9+=+21+
+21+=+21+
OK