15
ๅฟ็จ
ไพ้ก
13
ๆฌกใฎๅผใๅ ๆฐๅ่งฃใใใ
(37 (3x+y)(9x
20
20
่งฃ
a(b2-c2)+b(c2-aยฒ)+c(a-b2)
่งฃ่ชฌ ใใฎๅผใฏ,ฮฑ, b, c ใฎใฉใฎๆๅญใซใคใใฆใ2ๆฌกๅผใงใใใใใ
ใง,ไพใใฐ, ฮฑใซใคใใฆ้ในใใฎ้ ใซๆด็ใใใ
a(b2-c2)+b(c2-aยฒ)+c(aยฒ-b2)
=(-b+c)aยฒ+(62-cยฒ)a+(bc2-b2c)
=-(b-c)aยฒ+(b+c)(b-c)a-bc (b-c)
(1)
=-(b-c){aยฒ-(b+c)a+bc}
=-(b-c)(a-b) (a-c)
=(a-b)(b-c)(c-a)
็ทด2
็ทด็ฟ ๆฌกใฎๅผใๅ ๆฐๅ่งฃใใใ
21
ab(a-b)+bc(b-c)+ca(c-a)