根号1/7=（根号7）/7 根号28=根号（4*7）=2又根号7 根号700=（根号7*100）=10又根号7 根号1/7+根号28-根号700 =（根号7）/7+2*根号7-10*根号7 =（1/7+2-10）又根号7 =7又6/7*根号7
=根号7除以7+2乘根号7-10乘根号7=(1/7+2-10)乘根号7=-35/7乘根号7
