(m-n)(m+n)(m-n)(m+n)= (-0.5 - 0.3)(-0.5 + 0.3)(-0.5 - 0.3)(-0.5 + 0.3)= (-0.8)(-0.2)(-0.8)(-0.2)= 0.032
(1-a)(a-2)(3-a)(a-4)= (1-2)(2-2)(3-2)(2-4)= (-1)(0)(1)(-2)= 0
(m-n)(m+n)(m-n)(m+n)
= (-0.5 - 0.3)(-0.5 + 0.3)(-0.5 - 0.3)(-0.5 + 0.3)
= (-0.8)(-0.2)(-0.8)(-0.2)
= 0.032
(1-a)(a-2)(3-a)(a-4)
= (1-2)(2-2)(3-2)(2-4)
= (-1)(0)(1)(-2)
= 0