Question

1) 1+2+3+---+37 2)1+2+3+---+54 3) 4+8+12+16+---+48 4)5+10+15+20+---+75​

Answer 1

Explicație pas cu pas:

1) 1+2+3+...+37=37x38:2=703

2)1+2+3+...+54=55×55:2=1485

3) 4 +8 +12 +...+48=

=48 +44 +40 +...+ 4

n=numarul de termeni din suma

n=(48-4):4+1=12

=>2S=52×n=52×12=>S=52×6=312

4)5 +10 +15 +20 +...+75=

=75 +70 +65 +60 +...+ 5

n=(75-5):5+1=15

=>2S=80×n=80×15=>S=40×15=600