1)a•b = |a|•|b|•cos 60° = 5•6•1/2 = 15
2)n•m = (a+2b)(3a-b) = 3a²-ab+6ab-2b² = 3|a|²+5ab-2|b|² = 3•26+5•15-2•36 = 78+75-72 = 78+3 = 81
