lim x ---> 9 so ( x^(2) - 81 ) / ( (√x) - 3 ) solve limit?

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lim x ---> 9 so ( x^(2) - 81 ) / ( (√x) - 3 ) solve limit?

Be as detailed as possible...I'm not understanding how we get 108.

2007-09-08 21:45:19 · 2 answers · asked by gatortheone 1 in Science & Mathematics ➔ Mathematics

2 answers

Lim x→9 { (x² - 81) / (√x - 3) }

= Lim x→9 { (x + 9)(x - 9) / (√x - 3) }

= Lim x→9 { (x + 9)(√x + 3)(√x - 3) / (√x - 3) }

= Lim x→9 (x + 9)(√x + 3) = (9 + 9)(3 + 3) = 18*6 = 108

2007-09-08 22:00:59 · answer #1 · answered by Northstar 7 · 1⤊ 0⤋

x^2-81=(x-9)(x+9)
x-9=(sqrt x -3)(sqrt x+3)
Then simplify

2007-09-08 22:02:26 · answer #2 · answered by Theta40 7 · 0⤊ 0⤋