Question

Rezolvati in N: a) 2×{10+5{7+2(X-2)]}:10=13
b) 5x+10x+15x+...+50x=2750

Answer 1

Rezolvati in N: a) 2×{10+5[7+2(X-2)]}:10=13

2×{10+5(7+2X-4)]}:10=13

2×[10+5(3+2X)]:10=13

2×(10+15+10X)=13×10

2×(25+10X)=130

50+20X=130

20X=130-50

20X=120

X=6

b) 5x+10x+15x+...+50x=2750

5X(1+2+3+....+10)=2750

1+2+3+....+10=suma Gauss S=n(n+1)]:2=(10×11):2=55
5X×55=2750
5X=2750:55
5X=55
X=11