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1 . a ) Calculati 5 x + 7 y + 2 z , stiind ca x +  y = 123 si y + z = 257 .
     b ) Determinati x , stiind ca : ax + 3bx + 7x = 380 si 2a + 6b + 14 = 152 .


Răspuns :

a.5 x + 7 y + 2 z=5x+5y+2y+2z=5(x+y)+2(y+z)=5*123+2*257=615+514=1129

b.
 
2a + 6b + 14 = 152⇒2(a+3b+7)=152⇒a+3b+7=76
ax + 3bx + 7x = 380
x(a+3b+7)=380
x76=380
x=380:76
x=5