Question

Folosim metoda factorului comun calculati urmatoarea suma:
a)4+8+12+16+.....+396+400

Answer 1

4(1+2+3+.....+99+100)
4(100*101/2)=2*100*101=20200

Answer 2

$\displaystyle 4+8+12+16+...+396+400=4(1+2+3+4+...+99+100)= \\ \\ =4 \times \frac{100(100+1)}{2} =4 \times \frac{100 \times 101}{2} =4 \times \frac{10100}{2} =4 \times 5050=20200$