[问答题]
A uniform rectangular plate of lengtuib1f* sao k2 w+e()bpu- wjq,h l and width w has coefficient of qd594qn/uq.d cj ;ulc linear expans5uucc l49q j;ddqq/n.ion $\alpha$ 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.