According to the image, f(x)=0 has three roots, others have two roots, and the quadratic equation has two roots, so these three plus the other two are all symmetrical about x=2, one is 2, and the average value of the other two is 2, so x 1+x2+x3+x4+X5 = 2+4+.

f(x 1+x2+x3+x4+X5)= f( 10)= 3lg 2