y=(x-70-60)(3000-10x)
(1)令函数表达式y=kx+b{70k+b=3000{90k+b=1000k=-100,b=10000y=-100x+10000(2)w=(x-60)(-100x+10000) =-100x²+16000x-600000 =-100(x-80)²+40000当x=80元,利润最大,为40000元
