A.2^－2k                                                              B.2^－(2k－1)

C.－2^－(2k+1)                                                     D.2

C(2，y)與A(－1，－1)、B(1，3)兩點(diǎn)共線，則y的值是

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(2－)⁸展開式中不含x⁴項的系數(shù)的和為(　　)

 (－x)² 等于(　　)

A.                      B．－x

C．x                    D．x

 (－x)² 等于                                                (　　)

A.                          B．－x

C．x                        D．x