推 shiang00 :謝謝你!! 02/09 20:34
※ 引述《shiang00 (最近)》之銘言：
: 3. Find a number b such that the function from R to R defined by
: x^2 - 9
: --------- for x≠3
: ╭ x - 3
: f(x) = │
: ╰ b for x=3
: is continuous.
: 麻煩各位的指教了！ 謝謝!
lim f(x) = f(3)
x→3
x^2 - 9
lim ──── = b
x→3 x - 3
(x+3)(x-3)
lim ───── = b
x→3 x - 3
lim (x+3) = b
x→3
b = 6
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