(x 1-x2)？ =(x 1+x2)？ -4x 1x2=4m？ - 12m= 16

∴m=4 or m=- 1

When m=4, x? -2mx+3m=0 Two roots x 1=2, x2=6.

x？ -2mx+6m-9=0 These two roots are x3 = 3 and x4 = 5.

Built between two roots

When m=- 1, x? -2mx+3m=0 Two roots x 1=4, x2=- 1.

x？ -2mx+6m-9=0 These two roots are x3 =-5 and x4 = 3.

Obviously not true.

So m=4