A linear equation problem of compulsory 2 in senior high school mathematics

As shown in the figure, let the symmetry point of B about the straight line y=2x be B 1(a, b).

Then the midpoint of (1)BB 1 is on the axis of symmetry: (b+1)/2 = 2 * (a+3)/2;

(2)BB 1 perpendicular to the symmetry axis: (b-1)/(a-3) =-1/2;

The above two equations can be solved as a=-1 and b=3, so b 1 (- 1, 3),

Then the equation of straight line AB 1 can be obtained by two-point formula as (y-3)/(2-3) = (x+1)/(-4+1).

X-3y+ 10=0，

The simultaneous equations of y=2x, x=2 and y=4 can be solved.

That is, c (2 2,4).