-(-7-х)-(6+5х)=2(х-3)
(b-8)(b+3)=bкв-5b-24
Тождества

-(-7-х)-(6+5х)=2(х-3)7+х-6-5х=-4х+1-4х+1≠2(х-3)(b-8)(b+3)=b²-5b-24b²+3b-8b-24=b²-5b-24b²-5b-24=b²-5b-24