t²-3t+2=0 因式分解(t-1)(t-2)=0所以t=1秒上升到10米,而后继续上升,t=2秒时又落回到10米处,再下落到抛出点用配元法t²-3t+2=0
t²-3t+2=t²-3t+(3/2)^2-1/4=0
(t-3/2)^2=1/4
(t-3/2)^2=(1/2)^2
t-3/2=1/2or t-3/2=-1/2
t=2 ort=1还用英文。。。。。。。。。用用,没问题,表述简洁些,希望接受