.nf
TAB does not work:
.sp
.ta 0.5i +0.5i +0.5i
.EQ
x sub 1	+x sub 2	+s sub 1	=^10
.EN
.EQ
-2x sub 1		+s sub 1	=^42
.EN
.EQ
delim $$
.EN
.sp
Root sign line is shifted to the right side:
.sp
.EQ
sqrt {b sup 2 - 4ac}
.EN
.sp
Brackets are not aligned:
.sp
$P=R left [ 1^-^{1+1 sup n} over i right ]$