20题怎么解20题怎么解
20题怎么解
y黑=x²-2x=x²-2x+1-1=(x-1)²-1
y黄=(x-1)²-1+3=(x-1)²+2=x²-2x+3
y绿=(x-1-4)²+2=(x-5)²+2=x²-10x+27