一條f.3 maths題急,測驗用

1b)12(m - n)² - 22(m² - n²) + 10(m + n)²= 3 ( 4(m - n)² ) - 11 ( 2(m - n)(m + n) ) + 10 (m + n)²= 3 ( [2(m - n)]² ) - 11 ( 2(m - n) * (m + n) ) + 10 (m + n) ² ... (*)
Let 2(m - n) = a , (m + n) = b , put to (*) := 3 a² - 11 a b + 10 b²
By the result of a) , = (3a - 5b) (a - 2b)
= (3 * 2(m - n) - 5 * (m + n) ) ( 2(m - n) - 2(m + n) )= ( 6m - 6n - 5m - 5n ) ( 2m - 2n - 2m - 2n )= ( m - 11n ) ( - 4n)= - 4n(m - 11n)