【1】
(1/2)a"b + m = (1/2)ab( n + 2b )
= (1/2)abn + ab"
這就看到
(1/2)abn = (1/2)a"b
n = a
m = ab"
【2】
( x + 1 )( x + 2 )( x + 3 )( x + 4 ) + 1
= ( x + 4 )( x + 1 )( x + 2 )( x + 3 ) + 1
= ( x" + 5x + 4 )( x" + 5x + 6 ) + 1
= ( x" + 5x + 5 - 1 )( x" + 5x + 5 + 1 ) + 1
= ( x" + 5x + 5 )" - 1 + 1
= ( x" + 5x + 5 )"
【3】
( x - 4 ) 是 x" + mx - 12 的一個因式,那么
( x - 4 )( x + 3 )
= x" - 4x + 3x - 12
= x" - x - 12
m = -1
【4】
5 = 1 + 2 + 2
= 1 + 2 + 1X2
這樣 x = 1,y = 2；
或者 x = 2,y = 1.
【5】
a" - b" - c" - 2bc
= a" - ( b" + 2bc + c" )
= a" - ( b + c )"
三角形,兩條邊長的和,肯定大于第三條邊長,
那么
a" - ( b + c )" < 0