a^2(c^2-9)+4(c^2-9)= (c^2-9)(a^2+4)
Решение задания приложено
1) 2/3-8/23*(3/4+1.1/6)=2/3-8/23*3/4+8/23*7/6=2/3-2/23*3+4/23*7/3=2/3-6/23+28/69=2/3-(18+28)/69=2/3-46/69=(46-46)/69=0/69=0;
2) 5/26-6/5*10/9+12/7:8/7=5/26-2*2/3+12/8=5/26-4/3+2/8=5/26-(32+6)/24=5/26-38/24=5/26-19/12=5/26-1.7/12=-1(60-182)/312=-2.122/312=-2.61/156;
Cos^2a+sin^2a=1.
1+tg^2b=1+ sin^2b/cos^2b=1/cos^2b
(√3-√11)²:√33-7=3-2√33+11:√33-7=14-2√33:√33-7=-2(-7+√33):√33-7=-2