Question

Y=2+6+9+10+.....+60
Z=3+6+9+12+15+......150
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Answer 1

$Y = 2 + 6 + 8 + 10 + ... + 60 \\ Y = 2(1 + 2 + 3 + ... + 30) \\Y =2\cdot \frac{30 \cdot (30 + 1)}{2} \\ Y = 2\cdot15\cdot31 \\ Y = 30 \cdot 31 \\ Y = 930$

$Z = 3 + 6 + 9 + ... + 150 \\ Z = 3(1 + 2 + 3 + ... + 50) \\ Z = 3\cdot \frac{50\cdot(50 + 1)}{2} \\ Z = 3\cdot25\cdot51 \\ Z = 75\cdot51 \\ Z = 3825$

$\boxed{1+2+3+...+n=\frac{n\cdot(n+1)}{2}}$

Answer 2

Răspuns:

Bună, sper ca te am ajutat!!!