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daca x+2y=17 si y-3z=4, atunci calculati
a) x+3y-3z
b) 2x+5y-3z
c) (3x+6y) + (2y-6z)
d (2x+4y) * (x+4y-6z)


Răspuns :


a)  x+3y-3z=(x+2y)+y-3z=(x+2y)+(y-3z)=17+4=21

b) 2x+5y-3z=2x+4y+y-3z=2(x+2y)+(y-3z)=2*17+4=34+4=38

c) (3x+6y)+(2y-6z)=[3(x+2y)]+[2(y-3z)]=3*17+2*4=51+8=59

d) (2x+4y)*(x+4y-6z)=2(x+2y)*(x+2y+2y-6z)=2(x+2y)*[(x+2y)+2(y-3x)]=2*17*(17+2*4)=34*(17+8)=34*25=850