Question

URGENT 20 PUNCTE!!!!!
1) dacă a/b=c/d b*c=5 să calculeze 3bc+15/ad
2x/y=7/4 si x+y=99 calculați x si y

Answer 1

a/b=c/d rezulta ca a*d=b*c.

dar b*c=5 rezulta ca si a*d=5.adica

3bc+15/ad=3*5+15/5=15+3=18

2x/y=7/4 si x+y = 99.

rezulta ca 2x*4=7*y si x=99-y.

8x-7y=0

x=99-y

8(99-y)-7y=0  792-8y-7y=0  15y=792  y=792/15  y=52.8

x=99-52.8  x=46.2

sper ca-ti este de folos

Answer 2

a/b=c/d <=> $\frac{a}{b}= \frac{c}{d}$ => a*d = b*c deci 3bc+15/ad = 3*5+15/5=15+3=18
$\frac{2x}{y}= \frac{7}{4} =\ \textgreater \ y= \frac{4*2x}{7}= \frac{8x}{7}$
x+y=99
$x+ \frac{8x}{7}=99$
$\frac{15x}{7}=99 =\ \textgreater \ 15x=99*7 deci x=99*7/15=46,2$
46,2+y=99 => y=52,8