SOLUTION: I'm trying to brush up on my math skills 45 years after high school. Most of it is pretty basic but this one has me stumped. ( b + a ) / ab = 1 / f solve for b I've mashed

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Question 1116106: I'm trying to brush up on my math skills 45 years after high school. Most of it is pretty basic but this one has me stumped.
( b + a ) / ab = 1 / f
solve for b
I've mashed it all around but I just can't tease out the b. I even tried working backward from the answer. How is this done? The answer in the back of the book is:
b = fa / ( a - f ) or b = -fa / ( f - a )
if you're interested.
Thank you,
Jim
Found 2 solutions by ankor@dixie-net.com, MathTherapy:
Answer by ankor@dixie-net.com(22740)   (Show Source): You can put this solution on YOUR website!

cross multiply
f(b+a) = ab
fb + fa = ab
fb - ab = -fa
Factor out b
b(f-a) = -fa
b =
Answer by MathTherapy(10551)   (Show Source): You can put this solution on YOUR website!

I'm trying to brush up on my math skills 45 years after high school. Most of it is pretty basic but this one has me stumped.
( b + a ) / ab = 1 / f
solve for b
I've mashed it all around but I just can't tease out the b. I even tried working backward from the answer. How is this done? The answer in the back of the book is:
b = fa / ( a - f ) or b = -fa / ( f - a )
if you're interested.
Thank you,
Jim


ab = f(b + a) ------ Cross-multiplying

ab = bf + af

ab - bf = af

b(a - f) = af

 

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