algebra

posted by on .

-12x+10/5 = - x/20
I can't decide if I should cross multiply by -20 or just 20. The - is in the middle of the x and 20 (like a fraction)
I came up with 2 possible answers:
x=40/49 and x = 40/47

• algebra - ,

• algebra - ,

The answer I got using a calc is 2

• sign error - ,

(-12x+10)(-20)/5 = -x (-20/20)
I made a sign error here
48 x -40 = +x
47 x = 40
x = 40/47

• no way I get 2 - ,

Not for this problem

• algebra - ,

Is it (-12x+10) / 5

Or
-12x + (10/5)

?

• algebra - ,

scroll down Matts. I did it both ways.

• algebra - ,

I am not a big fan of the expression "cross multiply"
What you want to do here is multiply both sides, all terms by -20 (or 20 would work too)
FIRST THE WAY YOU TYPED IT (probably wrong)
-12(-20) x + 2(-20 ) = -x(-20)
240 x - 40 = 20 x
220 x = 40
x = 2/11
NOW WHAT I THINK YOU MEAN
(-12x+10)(-20)/5 = -x (-20/20)
48 x -40 = -x
49 x = 40
x = 40/49
PARENTHESES ARE IMPORTANT WHEN TYPING EQUATION ON A COMPUTER (because of order of operations)

typo - Damon, Friday, April 22, 2011 at 8:14pm

(-12x+10)(-20)/5 = -x (-20/20)
I made a sign error here
48 x -40 = +x
47 x = 40
x = 40/47