方法一：定义法证明：任取x1>x2>-1,则y(x1)-y(x2)=(x1²+2x1)-(x2²+2x2)=(x1²-x2²)+2(x1-x2)=(x1-x2)(x1+x2+2)∵x1>x2>-1∴x1-x2>0x1+x2+2>-1-1+2=0∴y(x1)-y(x2)>0∴y(x1)>y(x2)∴函数y=x²...