(m+1)² - 5(m+1)(m-1)+ 4(m-1)²
=【(m+1)² - 4(m+1)(m-1)+ 4(m-1)²】-(m+1)(m-1)
=【(m+1)-2(m-1)】²-m²+1
=【3-m】²-m²+1
=9-6m+m²-m²+1
=10-6m
=2(5-3m)
(m+1)² - 5(m+1)(m-1)+ 4(m-1)²
=【(m+1)² - 4(m+1)(m-1)+ 4(m-1)²】-(m+1)(m-1)
=【(m+1)-2(m-1)】²-m²+1
=【3-m】²-m²+1
=9-6m+m²-m²+1
=10-6m
=2(5-3m)