[SOLVED] algebra

Quote:

Originally Posted by dyr

how do you solve 1/x=1/t + 1/r ??

and -4<2 (x-3)< 8

Hello,

to 1.: You need a common denominator (which is here r*t):
$\frac{1}{x}=\frac{r+t}{r \cdot t}\ \Rightarrow \ x=\frac{r \cdot t}{r+t}$

to 2.: Split the inequalities into two single inequalities:
$-4<2 (x-3)< 8\ \Leftrightarrow \ -4<2(x-3)\ \ \wedge \ \ 2(x-3)<8$

$1 < x\ \wedge \ x < 7\ \Leftrightarrow \ 1<x<7$

Greetings

EB