PR
25
次の式を展開せよ。
③ (4x+3y)(16x?-12xy+9y°)
の(3a-b)(9a+3ab+6°)
(1)(3x+y)°=(3x)°+3(3x)?·y+3-3x·y°+y°
=27.x°+27.°y+9.xy"+y°
(2)(-m+2n)°=(1m)°+3(-m) 2n+3(-m)(2n)。+(2n)°
-m°+6m°n-12mn+8n°
ロ(a+b)°
=a°+3a°b+3ab°+ぴ
ロ(a+b)°
=a°+3a°b+3ab°+6°
ニー
別解(-m+2n)°=(2n-m)°
(a-b)
=a°-3a°b+3ab°-ぴ
3
=(2n)-3(2n)· m+3·2n·mーm
-8パー12mn"+6m°n-m°
=ーm+6m°n-12mn+8n°
3
を見つけ
(3) (4x+3y)(16x?-12xy+9y°)
=(4x+3y){(4x)-4x·3y+(3y)"}al
=(4x)°+(3y)°
=64.x°+27y°
ロ(a+b)(a-ab+16')
1(+|=+が