well, there are legalised "cheating" methods in maths by using
calculators
Example for O and A levels, Binomial Expansion and partial
fractions, you can always sub in some values of X to confirm LHS =
RHS
or for differentiation at As, you can also use the graphic
calculator to prove your answer numerically
;)
erm
it's been more than a decade since my A levels, but i'm pretty
sure the LHS=RHS proving questions aren't asking you if the
equation is correct.
Rather, you're supposed to prove WHY it's correct. Substituting
values to prove it should get you a zero.
Ditto for differentiation.