1) а²-16b² / 4ab : ( 1/4b - 1/a) = (a-4b)(a+4b) / 4ab * 4ab / a-4b = a+4b
a+4b = 3 5/13 + 4 * 4 2/13 = 3 5/13 + 16 8/13 = 19
2) х²-4х+3≥0
D = 16-12=4
х₁ = 4-2 / 2 = 1
х₂ = 4+2 / 2 = 3
\\\\\\\\\\ ///////////
---------.----------.-------->x
1 3
х∈(-∞; 1]∪[3; +∞)
Ответ: 1)