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# A couple questions

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1: The function h(x) is defined as:

{ (floor(4x)) if x < / = pi

h(x)={ 3-x            if pi < x

{ x^2           if 5.2 < x

Find h(h(sqrt2))

2: Find constants A and B such that

(x+7)/(x^2-x-2) = A/(x-2) + B/(x+1)

for all x such that x does not equal -1 and x does not equal 2. Give your answer as the ordered pair (A,B).

3: Suppose that  | a - b | + | b - c | + | c - a | = 20. What is the maximum possible value of | a - b |?

Thanks so much! Feel free to answer individually!

AnonymousConfusedGuy  Dec 15, 2017
edited by AnonymousConfusedGuy  Dec 15, 2017
edited by AnonymousConfusedGuy  Dec 15, 2017
Sort:

#1
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2: Find constants A and B such that

(x+7)/(x^2-x-2) = A/(x-2) + B/(x+1)

We can use partial fractions here

(x +7)  / [ ( x -2) (x + 1) ]   =    [ A (x + 1)  + B(x - 2) ] / [ ( x - 2) (x+1)]

And we can solve this

x + 7  =  A(x + 1)  + B(x - 2)   simplify

x + 7  = Ax + A  +  Bx  - 2B

x + 7  =  (A + B)x  + ( A - 2B)      equate coefficients

A + B  =  1

A - 2B  = 7          subtract the second equation from the first

3B  = -6

B = -2

So   A  + (-2)  =    1       ⇒  A  =  3

So    { A, B}  =  { 3, -2}

CPhill  Dec 15, 2017
#2
+2

Since the differences between the three variables are "absolute", then the maximum difference between a and b must be 10!!. You may assign any two values to them as long as they are separated by 10. And the value of c would be the average of the two. So, if we pick:

a =110, b=100 and c=105, then: | 110 - 100 | + | 100 - 105 | + | 105 - 110 | = 20

10         +          5            +        5             = 20

So the maximum of: a - b =10

Guest Dec 15, 2017
#3
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AnonymousConfusedGuy  Dec 15, 2017
#4
+81022
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OK......ACG

In your first  problem, you  have

floor (4x)   if   x

If x   is what  ???

Also......if  x > pi   ......  either of the other two functions might apply

Did you leave something out  ???

CPhill  Dec 15, 2017
#5
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Oh oops, I did! Fixed now!

AnonymousConfusedGuy  Dec 15, 2017
#6
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1.

h (h(sqrt 2) )

Since   sqrt 2 ≤  pi.......use the first function

So   floor  (4 * sqrt2)  =  floor ( ≈ 5.6)  =  5

So

h (h (sqrt 2))  =  h (5)

Since  5     is     > pi   but <  5.2

We use the second function, 3 - x

So

h (5)  =   3  -  5     =     - 2

CPhill  Dec 15, 2017
edited by CPhill  Dec 15, 2017
edited by CPhill  Dec 15, 2017

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