1.用简便计算:(1)49.9^2 +9.98+0.1^2(2)9999^2 +19999分解因式:4xy^2-4x^2y-y^3(4a^2 +1)^2 -16a^2

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1.用简便计算:(1)49.9^2 +9.98+0.1^2(2)9999^2 +19999分解因式:4xy^2-4x^2y-y^3(4a^2 +1)^2 -16a^2

1.用简便计算:(1)49.9^2 +9.98+0.1^2(2)9999^2 +19999分解因式:4xy^2-4x^2y-y^3(4a^2 +1)^2 -16a^2
1.用简便计算:
(1)49.9^2 +9.98+0.1^2
(2)9999^2 +19999
分解因式:
4xy^2-4x^2y-y^3
(4a^2 +1)^2 -16a^2

1.用简便计算:(1)49.9^2 +9.98+0.1^2(2)9999^2 +19999分解因式:4xy^2-4x^2y-y^3(4a^2 +1)^2 -16a^2
49.9^2 +9.98+0.1^2
=49.9^2 +2*49.9*0.1+0.1^2=(49.9+0.1)^2=2500
9999^2 +19999 =9999^2 +19999 =9999^2+2*9999*1+1^2=(9999+1)^2=10^8
4xy^2-4x^2y-y^3
=-y(y^2-4xy+4x^2)=-y(y-2x)^2
(4a^2 +1)^2 -16a^2
=16a^4+8a^2+1-16a^2
=16a^4-8a^2+1
=(4a^2 -1)^2

^这个符号是什么?

4xy^2-4x^2y-y^3
=y(4xy-4x^2-y^2)
=-y(y^2-4xy+4x^2)
=-y(2x-y)^2