Question

determinati nr natural x,daca:4+8+12+.......396=200x

Answer 1

4+8+12+...+396=200x  l:4
1+2+3+...+99=50x
$\frac{99x100}{2} = \frac{9900}{2} =4950$
4950=50x
x=$\frac{4950}{50} =99$

Answer 2

4+8+12+...+396=200x  l:4
4×(1+2+3+........+99)=200x
(1+2+3+........+99) suma Gauss cu formula de calcul S=[n(n+1)]:2=(99×100):2=4950

4×4950=200x
x=(4950×4):200
x=99