Question 193917
(7x^2-4x+3)  -  (5x^2 +3x -8)
usually  better  to  just  add,  avoids  sign  errors,
just  add  the  opposite
,
(7x^2 -4x +3)  + ( -5x^2 -3x +8)
,
2x^2 -7x +11 ,,,,,ANSWER
,

another  technique  is  to  use  vertical format,  just  line  up  powers, (still  like  add  opposite)
,
,,,,,,,,,,,,7x^2   -4x   +3
,,,,,,,,+,,-5x^2 -3x   +8
_________________________
,,,,,,,,,,,,,2x^2 -7x  +11