Question

fără ex 25
va rog
5 stele​

Answer 1

Răspuns:

Explicație pas cu pas:

a)

x+1+x+2+.......+x+50=(x+25)²+25

50x+1+2+....+50=(x+25)²+25

50x+50×51/2=x²+50x+625+25

x²+650=25×51 x²=1275-650 x²=625 x=25

b)1+3+5+.....+(2x-1)=100

∑(2k-1)=100 2k(k+1)/2-k=100 k²+k-k-100=0 k²=100

k=10