某林场拟定一7天植树任务:每一天都比前一天增派5人植树,但每人植树的棵树要比前一天少5棵.每人每天指数棵树相同.已知7天
2个回答

设第一天值了x棵树,用了y人

xy

(x-5)(y+5)=xy+5x-5y-25

(x-10)(y+10)=xy+10x-10y-100

(x-15)(y+15)=xy+15x-15y-225

(x-20)(y+20)=xy+20x-20y-400

(x-25)(y+25)=xy+25x-25y-625

(x-30)(y+30)=xy+30x-30y-900

7xy+105x-105y-2275=9974

7xy+105x-105y=12249