[问答题]
A uniform rectangular plate of length l and wid,ujmjyg-y p 9gvqs(*kf s0m :,th w 2erkphrq 88l))lx 6:fyzvmb8 has coefficient of linear expansion xzef)rh lbq)mp6828k 8vlr y:$\alpha$ Show that, if we neglect very small quantities, the change in area of the plate due to a temperature change $\Delta$T is $\Delta$A = 2$\alpha l w$$\Delta$T See Fig. 13–30.
