Răspuns:
18) a)2m+4n+6p=2×(m+p)+4×(n+p)=2×103+4×301=
=206+1204=
=1210
b)3m+6n+9p= 3×(m+p)+6×(n+p)=3×103+6×301=
=309+1806=
=2115
19) a) xz+xt+yz+yt=x(z+t)+y(z+t)=(z+t)×(x+y)
=68+75=143
b) xy+xt+yz+zt=x(y+t)+z(y+t)=(y+t)×(x+z)=
=91+45=136
20) a) 2+4+6+...+1000=2×(1+2+3+...+500)=2×500×501:2==250500
b) 3+6+9+...+2013=3×(1+2+3+...+671)=3×671×672:2=3×671×336=676.368
c) 5+10+15+...+500=5×(1+2+3+...+100)=5×100×101:2=5×50×101=5050×5=25250
d) 7+14+21+...+700=7×(1+2+3+...100)=7×100×101:2=7×50×101=350×101=35.350
Sper ca te-am ajutat!
