<span>287² - 287 * 48 + 239 * 713 = </span>239000
287*287=82369
287*48=13776
239*713=170407
82369 - 13776= 68593
68593+170407=239000
<span>73,4² + 73,4 * 17,2 - 90,6 * 63,4 = 906
73,4*73,4= 5387,56
73,4*17,2=1262,48
90,6*63,4=5744,04
5387,56+1262,48=6650,04
6650,04-5744,04=906
</span>