<span>3(5-4а)-(12а-7)= 15 -12а -12а+7 = 22-24а = 22 -24 * 0,5 = 22- 12 = 10
</span><span>6(3а+5)-(17+2а) = 18а +30 -17-2а = 16а + 13 = 16 *(-0,25) +13 = -4+13 = 9
</span>
7(4+с)-(3с-5) = 28 +7с - 3с+ 5 = 33 +4с = 33 +4*(-<u />) = 33 -3 = 30
Х2<span> + 12</span>х<span> + 36 = 0</span>
(х+6)2₂<span> = 0</span>
х+6 = 0
х<span> = -6
вроде правильно.
</span><span>
</span>
по формуле сокращённого умножения: (х-2)(х+2)