Вычислите : 1) 287²-287·48+239·713 2) 73,4²+73,4·17,2-90,6·63,4

287^2-287*48+239*713 = 287*(287-48) + 239*713 = 287 * 239 + 239*713 =  239*(287+713)=239*1000 = 239000 ============================================== 73.4^2+73.4*17.2-90.6*63.4 = 73.4*(73.4 + 17.2) = 73.4 * 90.6 - 90.6 * 63.4 =  90.6*(73.4-63.4)=90.6*10=906

x^2y+1-x^2-y

(x^2-1)y-x^2+1

(x-1)*(x+1)*(y-1)

0.8*(1-0.7)+(1-0.8)*0.7=0.24+0.14=0.38

ответ: 0.38

з.ы.вроде так)