Question

S=3+6+9+...127 vă rog să mă ajuți multumesc

Answer 1

$S = 3 + 6 + 9 + ... + 126$

$S = 3(1 + 2 + 3 + ... + 42)$

$S = 3 \times \frac{42(42 + 1)}{2}$

$S = 3 \times \frac{42 \times 43}{2}$

$S = 3 \times 21 \times 43$

$S = 2709$

$Formul\check{a}\:: 1 + 2 + 3 + ... + n = \frac{n(n + 1)}{2}$

Answer 2

S = 3 + 6 + 9 + ...... + 126

S = 3 × ( 1 + 2 + 3 + ...... + 42 )

S = 3 × 42 × ( 1 + 42 ) : 2

S = 3 × 21 × 43

S = 63 × 43

S = 2 709