Question

Решите уравнение: (x+141)+(x+134)+(x+127)+…+(x+1)=4200

Answer 1

пусть х+1=а₁   х+8=а₂
d=х+8-х-1=7
n=(x+141-x-1)/7  +1=21
S=(x+141+x+1)*21/2=4200
2x+142=4200*2/21
2x+142=400
2x=258
x=258/2
x=129