Question

Решите уравнение
2+4+6+8+...+х = 930

Answer 1

a1=2  a2=4  d=a2-a1=2
an=2+(n-2)*n=x
Sn=(a1+an)*n/2=930
(4+(n-1)*2)*n=1860
2n²+2n-1860=0
n²+n-930=0
n1+n2=-1 U n1*n2=-930
n1=-31 не удов усл
n2=30
x=a30=a1+29d
x=2+29*2=60