Let a1, a2, ..., an be fixed real numbers and define a function f(x) = (x−a1)(x−a2)...(x−an). What is limx→a1 f(x)?
For some a ≠a1,a2...an, compute limx→a f(x).
Here f(x) = (x−a1)(x−a2)...(x−an)
Now limx→a1f(x)=limx→a1(x−a1)(x−a2)...(x−an)
= (a1−a1)(a1−a2)...(a1−an)
= 0 ×(a−a1)(a−a2) ...(a1−an) = 0.
Also limx→af(x)=limx→a(x−a1)(x−a2)...(x−an)
= (a−a1)(a−a2)...(a−an)