SOLUTION: 3x+4=12x+5 This is what I"ve tried but don't know if I'm right. Plus I need to know how to check my work. 3x+4=12x+5 I saw somewhere that I make the 4 a - why do I make it

Algebra ->  Linear-equations -> SOLUTION: 3x+4=12x+5 This is what I"ve tried but don't know if I'm right. Plus I need to know how to check my work. 3x+4=12x+5 I saw somewhere that I make the 4 a - why do I make it       Log On


   

Question 988218: 3x+4=12x+5
This is what I"ve tried but don't know if I'm right. Plus I need to know how to check my work.
3x+4=12x+5 I saw somewhere that I make the 4 a - why do I make it a negative?
then add 4 to both sides
3x=12x+9 then divide all by 3
x=4x+3
Where do I go from here and please show me how to check my work. Thank you and God bless.
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39838) About Me  (Show Source):
You can put this solution on YOUR website!
Isolate the variable, arranging the terms of x on one side of the equation and all
the plain numbers on the other side of the equation. USE INVERSE PROPERTIES OF REAL NUMBERS and
the PROPERTIES OF EQUALITY.

3x%2B4=12x%2B5
3x%2B4%2B%28-4%29=12x%2B5%2B%28-4%29        Additive Inverse of +4, Addition Prop of Eqlty
3x=12x%2B1                    Computations, simplifications
3x%2B%28-12x%29=12x%2B1%2B%28-12x%29      Additive Inverse of +12x, Addition Prop of Eqlty
-9x=12x%2B%28-12x%29%2B1            Add terms of x, Commutative Property of Equality
-9x=1                       Computation
-9x%28-1%2F9%29=1%2A%28-1%2F9%29             Multiplicative Inverse of -9, Multiplication Prop of Eqlty
highlight%28x=-1%2F9%29                      Simplifications, having used multiplicative inverse

The solution process should be straightforward, and in practice, can be done in fewer steps.

Use the solution found for x to check in the original equation to see if it works.

Answer by MathTherapy(10858) About Me  (Show Source):
You can put this solution on YOUR website!
3x+4=12x+5
This is what I"ve tried but don't know if I'm right. Plus I need to know how to check my work.
3x+4=12x+5 I saw somewhere that I make the 4 a - why do I make it a negative?
then add 4 to both sides
3x=12x+9 then divide all by 3
x=4x+3
Where do I go from here and please show me how to check my work. Thank you and God bless. 
  3x + 4 = 12x + 5
      3x = 12x + 1 --- Subtracting 4 from both sides in order to ISOLATE 3x
3x - 12x = 1 --------- Subtracting 12x from both sides to isolate x
    - 9x = 1
      x+=+1%2F%28-+9%29 --------> highlight_green%28x+=+-+1%2F9%29


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Check
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Since x+=+-+1%2F9, substitute this value into the original equation

Therefore, 3x + 4 = 12x + 5 becomes:

3%28-+1%2F9%29+%2B+4+=+12%28-+1%2F9%29+%2B+5

cross%283%29%28-+1%2F3cross%289%29%29+%2B+4+=+4cross%2812%29%28-+1%2F3cross%289%29%29+%2B+5

-+1%2F3+%2B+4+=+-+4%2F3+%2B+5

3%262%2F3+=+-+1%261%2F3+%2B+5 

3%262%2F3+=+3%262%2F3 (TRUE)