[Toán 8] Hằng đẳng thức đáng nhớ

T

thaolovely1412

1. Tính:
a, [TEX](2x + y^2 )^3= (2x)^3+(y^2)^3+3(2x)^2y^2+3.2x.(y^2)^2=8x^3+y^6 +12x^2y^2+6xy^4[/TEX]
b, ([TEX]3x^2 - 2y)^3= (3x^2)^3-3.(3x^2)^2.2y+3.3x^2.(2y)^2-(2y)^3= 27x^5-54x^4y+36x^2y^2-8y^3[/TEX]
c, Chưa rõ đề
 
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H

huy14112

a)$(2x + y^2)^3=(2x)^3+3(2x)^2y^2+3.2x.(y^2)^2+(y^2)^3$

$=8x^3+12x^2y^2+6xy^4+y^6$

b)$(3x^2 - 2y)^3=(3x^2)^3-3(3x^2)^22y+3.3x^2.(2y)^2-(2y)^3$

$=27x^5-54x^4y+36x^2y^2-8y^3$
 
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