当A=1,Y=-2时,代数式X-(X+Y)+(X+2Y)-(X+3Y).-(X+99Y)值是( )

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当A=1,Y=-2时,代数式X-(X+Y)+(X+2Y)-(X+3Y).-(X+99Y)值是( )
当A=1,Y=-2时,代数式X-(X+Y)+(X+2Y)-(X+3Y).-(X+99Y)值是( )

当A=1,Y=-2时,代数式X-(X+Y)+(X+2Y)-(X+3Y).-(X+99Y)值是( )
x -(x + y )+(x + 2y) - (x + 3y) ...+ (x + 98y)- (x + 99y)
= [x -(x + y )] + [(x + 2y) - (x + 3y)] + ...+ [(x + 98y)- (x + 99y)]
= (-y)×50
= 2×50
= 100