the answer given in my book is 4b-3b=6+4, b= 10. but my conclusion is 4b-3b=-4+6, = -10. when do i apply positive, and when for negative?

Expert Answers
sheryll-pickett eNotes educator| Certified Educator

tx for responding to my math problem. the original problem is:-

Given the formula D/B = d+b/d-2b,

a) find B when d=1, b=3 and D=4

b) find b when B=3, D= -2 and d=2

 

This is how I would do them.

4/B = 1 + 3/1 - 2*3

Remember to do all the multiplication first.

4/B = 1 + 3/1 - 6

3/1 is the same as 3 so rewrite as

4/B = 1 + 3 - 6

Now do your addition and subtraction from left to right

4/B = -2

Undo division with multiplication

4 = -2B

Undo multiplication with division

4/(-2) = B

-2 = B because a positive divided by a negative is a negative.

sheryll-pickett

Apr 23 '10
11:26 AM

For the second equation...
-2/3 = 2 + b/2 - 2*b

I would eliminate the fractions by multiplying by the common denominator , in this case 6, on both sides of the equal sign.

6(-2/3) = (2 + b/2 - 2*b)6

By doing that you have a much simpler equation to work with.

-4 = 12 + 3b - 12b

Now it is easier to combine the like terms,3b - 12b.

This will give you the equation

-4 = 12 - 9b

Subtract 12 from both sides of the equal sign.
and you have

-16/(-9) = b

simplify your negatives and you get

16/9

I hope this helps...let me know if you need more information.

sheryll-pickett eNotes educator| Certified Educator

What was the original problem?????