how do you solve 1/x=1/t + 1/r ??
and -4<2 (x-3)< 8
Hello,Originally Posted by dyr
to 1.: You need a common denominator (which is here r*t):
$\displaystyle \frac{1}{x}=\frac{r+t}{r \cdot t}\ \Rightarrow \ x=\frac{r \cdot t}{r+t}$
to 2.: Split the inequalities into two single inequalities:
$\displaystyle -4<2 (x-3)< 8\ \Leftrightarrow \ -4<2(x-3)\ \ \wedge \ \ 2(x-3)<8$
$\displaystyle 1 < x\ \wedge \ x < 7\ \Leftrightarrow \ 1<x<7$
Greetings
EB