a, A= (a+b)^3 + (a – b )^3 b, B= ( x – y )^3 – 3.(x – y ) z^ 2 – z^3 c, C= 6.(c -d ).(c+d) ^2 + 12. ( c-d)^2. (c+ d) + ( c+d)^3 + 8 ( c-d) ^

0 bình luận về “a, A= (a+b)^3 + (a – b )^3 b, B= ( x – y )^3 – 3.(x – y ) z^ 2 – z^3 c, C= 6.(c -d ).(c+d) ^2 + 12. ( c-d)^2. (c+ d) + ( c+d)^3 + 8 ( c-d) ^”

1. Đáp án:

    $a)
   A=2a^3+6ab^2\\
   b)
   B=(x-y-z)^3\\
   c)
   C=(3c-d)^3\\
   d)
   D=u^3+6uv^2-v^3\\
   e)
   E=8c^3$

   Giải thích các bước giải:

    $a)
   A=(a+b)^3+(a-b)^3\\
   =a^3+3a^2b+3ab^2+b^3+a^3-3a^2b+3ab^2-b^3\\
   =2a^3+6ab^2\\
   b)
   B=(x-y)^3-3(y-x)^2z+3(x-y)z^2-z^3\\
   =(x-y)^3-3(x-y)^2z+3(x-y)z^2-z^3\\
   =(x-y-z)^3\\
   c)
   C=6(c-d).(c+d)^2+12(c-d)^2.(c+d)+(c+d)^3+8(c-d)^3\\
   =(c+d)^3+3.(c+d)^2.2(c-d)+3.(c+d).\left [ 2(c-d) \right ]^2+\left [ 2(c-d) \right ]^3\\
   =\left [ c+d+2c-2d \right ]^3\\
   =(3c-d)^3\\
   d)
   D=(u-v)^3+3uv(u+v)\\
   =u^3-3u^2v+3uv^2-v^3+3u^2v+3uv^2\\
   =u^3+6uv^2-v^3\\
   e)
   E=3(c-2d).(c+2d)^2+3(c-2d)^2.(c+2d)+(c+2d)^3+(c-2d)^3\\
   =(c+2d)^3+3(c+2d)^2(c-2d)+3(c+2d)(c-2d)^2+(c-2d)^3\\
   =(c+2d+c-2d)^3\\
   =(2c)^3\\
   =8c^3$

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