differentiablity and deribative

can anyone prove the following?
for the functions
f(x)= x^2 -3x + 8 if x>1
2x^2 + x+3 if x =<1

show using delta-epsilon property that f(x) is differentiable at every
pt except x not equal to 1
and show that f(x) is not differentiable at x=1

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