Analysis: Based on AB, if you sit on the high side of AB through C, the height is C's ordinate 3.

Abscissa of radix = | abscissa of a-b |=|4-( 1-x)|

Area = base x height /2=|4-( 1-x)|X3/2=6.

So x= 1.

Answer: (4-( 1-x))*3/2=6.

x= 1