Question

Determinati valorile reale ale lui x din: x-1 / 2 = 18 / x-1

Answer 1

La fel ca si la exercitiul precedent care ti l-am aratat  :)
2 ori 18=36,nu?
2x-2=36.
=>2x=36-2
2x=34
x=34:2
x=17.

Answer 2

$\displaystyle \frac{x-1}{2} = \frac{18}{x-1} \\ (x-1)(x-1)=18 \cdot 2 \\ x^2-x-x+1=36 \\ x^2-2x+1=36 \\ x^2-2x+1-36=0 \\ x^2-2x-35=0 \\ (x+5)(x-7)=0 \\ x+5=0 \\ x=0-5 \\ x=-5 \\ x-7=0 \\ x=0+7 \\ x=7 \\ S=\{-5;7\}$