Dacă 6 supra x = y supra 5, determinați valoarea expresiei 128 - 3xy
![Dacă 6 Supra X Y Supra 5 Determinați Valoarea Expresiei 128 3xy class=](https://ro-static.z-dn.net/files/db1/2a8b0dbda5fb414b2bc9c7cfe22ff4c7.jpg)
[tex]\it \dfrac{6}{x}=\dfrac{y}{5} \Rightarrow xy=5\cdot6 \Rightarrow xy=30\ \ \ \ \ \ (*)\\ \\ \\ 128-3xy\ \stackrel{(*)}{=}\ 128-3\cdot30=128-90=38[/tex]
[tex] \frac{6}{x} = \frac{y}{5} [/tex]
Aplicăm formula :
[tex] \frac{a}{b} = \frac{c}{d} < = > a \times d = b \times c[/tex]
[tex] \frac{6}{x} = \frac{y}{5} < = > x \times y = 6 \times 5 = > x \times y = 30[/tex]
[tex]128 - 3xy = 128 - (3 \times 30) = 128 - 90 = \huge \boxed{ \red{38} } {} [/tex]