Question

Daca x+y=8 si y+2z=5 Calculati x+13y+16z si x+22y+2z

Answer 1

x+y=8 <=> x=8-y
y+2z=5 <=> 2z=5 - y

deci înlocuim:
1) 8-y+13y+16*2 (5-y)= 0<=> 8+12y+32(5-y) =0 <=> 8+12y + 160-32y= 0 <=>168+20y = 0 <=> 20y=168 <=> y= 5/42
$\frac{20}{168} = \frac{5}{42}$

2) x+22y+2z =0 <=> 8-y + 22y +2*2(5-y) = 0 <=> 8+21y+4(5-y) =0 <=> 8+21y + 20- 4y=0 <=> 28+17y=0 <=> 17y=28 <=>y = 17/28


$\frac{17}{28}$