(a-4b)(4b+a) при a=1.2, b=-0.6
(1.2-4×(-0.6))×(4×(0.6)+1.2)= 3.6×(-1.2)=-4.32
(a-4b)(a+4b)=a²-4b²=1.44-4·0.36=1.44-1.44=0