Question

studying for an exam and would like someone to check my answers. Thanks
#9 (a)
S-r/1-r^n=a

(b)
ay/a-x=b

(c)
Aa/a+A=b

questions are in the attachment

Answer 1

hmm i think the first one might be wrong
you start with
\[S=\frac{a(1-r^n)}{1-r}\]
\[S(1-r)=a(1-r^n)\]
\[\frac{S(1-r)}{1-r^n}=a\]

Answer 2

ok thank you! that actually makes more sense.

Answer 3

the other two look correct?

Answer 4

\[\frac{x}{a}+\frac{y}{b}=1\]
\[\frac{x}{a}=1-\frac{y}{b}\]
\[\frac{x}{a}=\frac{b-y}{b}\]
\[\frac{a}{x}=\frac{b}{b-y}\]
\[a=\frac{bx}{b-y}\] is what i get

Answer 5

lol. @satellite73 It says solve for b.

Answer 6

ok fine

Answer 7

make the appropriate changes

Answer 8

so then mine was correct?

Answer 9

B is correct. Third one, this is what I got:
A(a + b) = a - b
Aa + Ab = a - b
-Ac - Ab + a = b
Ab + b = a - Ac
b(A + 1) = a - Ac
b = (A - Ac)/(A + 1)

Answer 10

i kind of lost you at the 3rd step, do you mean a instead of c and I'm not sure why you changed the sign?

Answer 11

Oh ok.
Aa + Ab = a - b
Aa + Ab - a = -b
Then you divide both sides by -1 which flips all of the signs.

Answer 12

is it to keep the b positive since thats what I'm solving for?

Answer 13

Yeah. I did it to keep b positive.

Answer 14

so what i got is -Aa+a/1-A=b…thats correct?