y=(60+6x)(120-6x)
=7200-360x+720x-36x²
=-36x²+360x+7200
=-36(x²-10x)+7200
=-36(x²-10x+25)+7200+900
=-36(x-5)²+8100
a=-36,h=5,k=8100
提示:运用配方法解
y=(60+6x)(120-6x)
=7200-360x+720x-36x²
=-36x²+360x+7200
=-36(x²-10x)+7200
=-36(x²-10x+25)+7200+900
=-36(x-5)²+8100
a=-36,h=5,k=8100
提示:运用配方法解