Ab=ΙaΙ*ΙbΙcos(a;b)=3*4*cos(2π/3)=12*(-1/2)=-6
a²=ΙaΙ*ΙaΙ=3*3=9
b²=ΙbΙ*ΙbΙ=4*4=16
(a+b)²=a²+2*a*b+b²=9+2*(-6)+16=13
(3a-2b)(a+2b)=3a²+6ab-2ab-4b²=3a²+4ab-4b²=3*9+4*(-6)-4*16=27-24-64=-61
(a-b)²=a²-2ab+b²=9+12+16=37
(3a+2b)²=9a²+12ab+4b²=9*9+12*(-6)+4*16=81-72+64=73