#12
18a^4 + 21a² : 3a² + 5a(2a+1/a) = 6a²+7 -10a²-5 = -4a²+2
ответ С
#13
(a+2b)(a-2b)(a²+4b²) = (a²-4b²)(a²+4b²) = a^4 - 16b^4
A
#14
(-0.2)^5 / (-0.1)^4 = (-2/10)^5 : (-1/10)^4 = -2^5 / 10^5 : 1 / 10^4 = -2^5 / 10^5 * 10^4 / 1 = -32 / 10 = -3.2
A
#15
-(-3)³ * (1/3)² = -(-27) * 1/9 = 27/9 = 3
B
#16
(5.2)³ / (1.3)² = (4*1.3)³ / 1.3² = (4³ * 1.3³) / 1.3² = 4³ * 1.3 = 64 * 1.3 = 83.2
C