Saturday, January 26, 2008

Calculus One








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5 comments:

Anonymous said...

Find the number a such that the limit exist?

lim (5x^2+ax+a+5)/(x^2-x-6)
x->-2

123edu said...

The denominator can be factor as (x-3)(x+2).

This means that the numerator should preferably contain a factor of (x+2) so we can cancel (x+2) and limit will exist when x approaches to -2.

So, we have
(Eq#1):
5x^2 + ax + (a+5) = 0

Substitute x = -2 in (Eq#1).
20 - 2a + a + 5 = 0
a = 25

Which gives us
5x^2+25x+30= (5x+15)(x+2)

So the new function

lim (5x^2+ax+a+5)/(x^2-x-6)
x->-2

becomes lim (5x+15)(x+2)/(x-3)(x+2)
x>-2

= lim (5x+15)/(x-3) = -1
x>-2

Therefore, a = 25.

Anonymous said...

derivative of tan(t^2 - t)

123edu said...

derivative of tan(t^2 - t) =

(2t-1)[sec^2(t^2 - t)]

Note: You must use chain rule.

Anonymous said...

what is the domain of

1/square root of (x+6)

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