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Question
Find the intervals in which the following functions are strictly increasing or decreasing:
x2 + 2x − 5
Solution
We have f (x) = x2 + 2x - 5
f (x) is being a polynomial is continuous and derivale on R.
Differentiating w.r.t.x, we get
For increasing, f (x) >0
= 2x + 2 >0
= x > -1
For decreasing f (x) < 0
= 2x + 2 <0
= x < -1
f (x) is strictly decreasing for x <-1
f (x) is strictly increasing for x > -1
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