当x=2和x=﹣1时,代数式x2+mx+n的值都为0,则m=( ),n=( ).
﹣1;﹣2
I don't have a partner _______. [ ]
A、to practice English
B、practice English
C、practicing English with
D、to practice English with
钻孔时,主要关键技术是()和()问题。