Question

1,43+1,43×2+1,43×3+.........+1,43×11

Answer 1

[tex]1,43+1,43\cdot 2+1,43\cdot 3+_{\dots}+1,43\cdot 11=\\ 1,43(1+2+3+_\dots}+11)=\\ \text{Pentru suma din paranteza aplicam formula lui Gauss:}\\ 1,43\cdot \dfrac{11\cdot 12}{2}=\\ 1,43\cdot 11\cdot 6=\boxed{94,38}[/tex]