!"# = = = ⇒ = = = !"#$ % &#! #'()*+% ,# /0# 1# ⇒ $%&'()&*+,!- (23#)456 = = b, TÝnh M N – a, M + N = (x 2 – 2xy + y 2 ) + (y 2 + 2xy + x 2 + 1) = x 2 – 2xy + y 2 + y 2 + 2xy + x 2 + 1 = (x 2 + x 2 ) + ( -2xy + 2xy) + (y 2 + y 2 ) + 1 = 2x 2 + 2y 2 + 1 a, M - N = (x 2 – 2xy + y 2 ) - (y 2 + 2xy + x 2 + 1) = x 2 – 2xy + y 2 - y 2 - 2xy - x 2 - 1 = (x 2 - x 2 ) + ( -2xy - 2xy) + (y 2 - y 2 ) - 1 = - 4xy - 1 ./01234 $%&'()&*+,!- (73#)4589 9 : ;<=98 >89 = x 2 2y + xy + 1 + x– 2 + y x– 2 y 2 1– = (x 2 + x 2 ) + (-2y + y) + (1 - 1) + xy x– 2 y 2 = 2x 2 - y + xy x– 2 y 2 VËy: C = 2x 2 y + xy x– – 2 y 2 = x 2 + y - x 2 y 2 - 1 - x 2 + 2y - xy - 1 = (x 2 - x 2 ) + (y + 2y) + (-1 - 1) - xy - x 2 y 2 = 3y - 2 - xy - x 2 y 2 VËy C = 3y - 2 - xy - x 2 y 2 Gi¶i a, V× C = A + B Ta cã A + B = (x 2 2y + xy + 1) + (x– 2 + y x– 2 y 2 - 1) ⇒b, Tõ C + A = B C = B - A Ta cã: B - A = (x 2 + y - x 2 y 2 - 1) - (x 2 - 2y + xy + 1) ./01234 $%&'()&*+,!- $%&5(&67!,!- (?%#-@A<B=" 1==: > 5 5 C C D D 1=:=: 66D 66D 66D 66D 66D>*=6 ==:'(E FF:: = : E = =5:5:=: G?#-@A1==:H(: ./01234 >=:=:'(E :F:: F : : 5F : 5 : CF : C : D : D $%&'()&*+,!- $%&5(&67!,!- (#-@A<B=" 1==: > 5 5 C C D D 1=:=: 66D 66D 66D 66D 66D>*=6 == G?#-@A1=:=:H( ./01234 E 66D 66D 66D 66D + 2008 9 66I F 66D F 66D 66I + 2008 $%&'()&*+,!- $%&5(&67!,!- (#-@A<B=" 1==: > 5 5 C C D D 1=:=: 66D 66D 66D 66D 66D>*=6 9 66I F 66D F 66D 66I + 2008 V× x - y = 0 ta cã x 2008 .0 + y 2008 .0 + 2008 = 2008 ./01234 9 66D 66D 66D $%&'()&*+,!- $%&5(&67!,!- 89:&; :J<'K#>LM,# # -@A<,>N"F :O(<>(573P-#5 :QR<H1>(?%SH(< ./01234 ./01234 ⇒ Bµi 34 Sgk/ 40: TÝnh tæng c¸c ®a thøc: a, P = x 2 y + xy 2 5x– 2 y 2 + x 3 vµ Q = 3xy 2 x– 2 y + x 2 y 2 b, M = x 3 + xy + y 2 x– 2 y 2 2 – vµ N = x 2 y 2 + 5 y– 2 Gi¶i a, P + Q = (x 2 y + xy 2 – 5x 2 y 2 + x 3 ) + ( 3xy 2 – x 2 y + x 2 y 2 ) = x 2 y + xy 2 – 5x 2 y 2 + x 3 + 3xy 2 – x 2 y + x 2 y 2 = (x 2 y – x 2 y ) + (xy 2 + 3xy 2 ) + (- 5x 2 y 2 + x 2 y 2 ) + x 3 = 4xy 2 – 4x 2 y 2 + x 3 b, M + N = (x 3 + xy + y 2 – x 2 y 2 - 2) + (x 2 y 2 + 5 – y 2 ) = x 3 + xy + y 2 – x 2 y 2 – 2 + x 2 y 2 + 5 – y 2 = (y 2 – y 2 ) + ( -x 2 y 2 + x 2 y 2 ) +( -2 + 5)+ x 3 + xy = 3 + x 3 + xy ⇒ 8= = : =: 8: =( )( )( ) E8= = = =( )()( )(:) ./01234