S=60t-1.5t的平方?
求S的最大值
S=60t-1.5t^2
= -1.5(t^2-40t)
= -1.5(t^2-40t+400-400)
= -1.5(t-20)^2 +600
=600-1.5(t-20)^2
因为(t-20)^2≥0,所以当 t=20时,S有最大值600
S=60t-1.5t的平方?
求S的最大值
S=60t-1.5t^2
= -1.5(t^2-40t)
= -1.5(t^2-40t+400-400)
= -1.5(t-20)^2 +600
=600-1.5(t-20)^2
因为(t-20)^2≥0,所以当 t=20时,S有最大值600