# Thread: I don't see how my book solved for x.... can anyone help?

1. ## I don't see how my book solved for x.... can anyone help?

x=ay
y=x+10
plugging it in x= a(x+10)

the book SAYS solving for x yields x= 10a/(1-a)

for the life of me I can't see how they got that.

I tried multiplying by its reciprocal, working around it.... I just cant see it for the life of me.

the book's solution doesn't show this step. is there something really basic I'm overlooking?

2. x=ay
y=x+10
so
x=a(x+10)
x=ax+10a
x-ax=10a
x(1-a)=10a
x=(10a)/(1-a)

3. Originally Posted by NotTooKeen
x=ay
y=x+10
plugging it in x= a(x+10)

the book SAYS solving for x yields x= 10a/(1-a)

for the life of me I can't see how they got that.

I tried multiplying by its reciprocal, working around it.... I just cant see it for the life of me.

the book's solution doesn't show this step. is there something really basic I'm overlooking?
$\displaystyle x = a(x + 10)$

$\displaystyle x = ax + 10a$

$\displaystyle x - ax = 10a$

$\displaystyle x(1 - a) = 10a$

$\displaystyle x = \frac{10a}{1 - a}$.

4. oh wow that was so simple I can't believe it.

do you guys have any tips on trying to catch obvious things like that?

I'm so oblivious sometimes, but I have a study sheet and go over the rules every day. I just manage to overlook them somehow...

thanks for the help, by the way

5. Originally Posted by NotTooKeen
oh wow that was so simple I can't believe it.

do you guys have any tips on trying to catch obvious things like that?

I'm so oblivious sometimes, but I have a study sheet and go over the rules every day. I just manage to overlook them somehow...

thanks for the help, by the way
Lots and lots of practice.