Question

Se stie ca: x+y = 23 si z = 15. Calculati xz + yz
se stie ca: ab + ac = 420 si b+c = 14 aflati a
se stie ca: ab + ac + a = 165 si b + c= 10. aflati a.
daca a b c sunt numere naturale si a + b +c = 18 iar 2a + b + 2c = 25 atunci calculati (a + c) . (3a + 2b+3c)
Ofer 11 puncte + Coroana!

Answer 1

1.x+y=23
z=15
xz+yz=>z(x+y)=>15*23=345

2.ab+ac=420
b+c=14
a(b+c)=420=>a*14=420=>a=420:14=>a=30

3.ab+ac+a=165
b+c=10=>a(b+c+1)=165
a*11=165=>a=165:11=>a=15

4.a+b+c=18
2a+b+2c=25
(a+c)(3a+2b+3c)

a+b+c=18
2a+b+2c=25
-2a-2b-2c=-36
2a+b+2c=25
b=11
2(a+c)+11=25
2(a+c)=14=>a+c=7
(a+c)(3a+2b+3c)=7(3*7+2*11)=>7*(21+22)=>7*43=301