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4.设(5x-x)n的展开式的各项系数之和为M,而二项式系数之和为N,且M-N=992。则展开式中x2项的系数为( )
A.250 B.-250 C.150 D.-150
联想:(1)已知(1-2x)6=a0+a1x+a2x2+------+a6x6,则+…+的值( )
A.1 B.26 C.35 D.36
(2)设(2x+)=a0+a1x+a2x2+a3x3+a4x4,则(a0+a2+a4)2-(a1+a3)2的值为( )
A.2 B.-2 C.1 D.-1
(3)已知(x+xlgx)5展开式中第3项为106,则x的值为( )
A.10 B.100 C.10或10 D.10
(4)若(x+)n的展开式中第三项系数为36,则自然数n的值为_____________.