Find the coordinates of the stationary points on each curve(in each equation).1.y=x^2+2x
2.y=4x^3+3x^2+2
3.y=2x+3+8/x
4.y=x^3-9x^2-21x+11
5.y=9x^2/3-2x+5
Please provide full working out, thanks.
Answers
y=x²+2x
we have to calculate the first derived
y´=2x+2
we equal to "0" the first derived and find out the value of "X"
2x+2=0
x=-2/2=-1
we have to calculate de second derived
y´´=2>0 ⇒we have a minimun at x=-1
we calculate y
y=(-1)²+2(-1)=1-2=-1
Answer: we have a minimum at (-1,-1)
2)
y=4x³+3x²+2
we have to calculate the first derived
y´=12x²+6x
we equalize to "0" the first derived and find out the value of "X"
12x²+6x=0
6x(2x+1)=0
6x=0 ⇒x=0
2x+1=0 ⇒x=-1/2
we have to calculate de second derived
y´´=24x+6
y``(0)=24(0)+6=6 >0 ⇒we have a minimun at x=0
y``(-1/2)=24(-1/2)+6=-12+6=-6 ⇒we have a maximum at x=-1/2
we calculate y
if x=0, y=2
if x=-1/2; y=4(-1/2)³+3(-1/2)²+2=9/4.
we have to equalize the second derived to "0" and find out the value of "x"
24x+6=0
x=-6/24=-1/4; in x=-1/4 we have an inflection point.
y=4(-1/4)³+3(-1/4)²+2=31/16
Answer: we have a minimum at (0,2), a maximum at (-1/2, 9/4) and a inflection point at (-1/4, 31/16).
3.
y=2x+3+8/x
y=(2x²+3x+8)/ x
we have to calculate the first derived
y´= [(4x+3)x-(2x²+3x+8)] / x²=(4x²+3x-2x²-3x-8) / x²=(2x²-8)/x²
we equal to "0" the first derived and find out the value of "X"
(2x²-8) / x²=0
2x²-8=0
x=⁺₋2
we have to calculate de second derived
y´´=[(4x)x²-2x(2x²-8)] / x⁴=(4x³-4x³+16x)/x⁴)=16/x³
y``(-2)=16/(-2)³=-2>0 ⇒ at x=-2 exist a maximum
y´´(2)=16/(2)³=2<0 ⇒ at x=2 exist a minimum
we calculate y
y(-2)=-4+3-4=-5
y(2)=4+3+4=11
Answer: we have a maximum at (-2,-5 ) and a minimun at (2,11)
4)
y=x³-9x²-21x+11
we have to calculate the first derived
y´=3x²-18x-21
we equal to "0" the first derived and find out the value of "X"
3x²-18x-21=0
x²-6x-7=0
x=[6⁺₋√(36+28)]/2=(6⁺₋8)/2
x₁=-1
x₂=7
we have to calculate de second derived
y´´=6x-18
y``(-1)=-6-18=-24<0 ⇒at x=-1 exist a maximum
y´´(7)=42-18=24>0 ⇒ at x=7 exist a minimum.
we calculate y
y(-1)=-1-9+21+11=22
y(7)=343-441-147+11=-234
We equalize the second derive to 0, and find out the value of "x"
6x-18=0
x=3 in x=3 exist an inflection point
y=27-81-63+11=-106
Answer: we have a minimum at (7,-234), a maximum at (-1,22) and an inflection point at (3,-106).
5)
y=9x²/³-2x+5
we have to calculate the first derived
y´=6x⁻¹/³-2
we equal to "0" the first derived and find out the value of "X"
6x⁻¹/³-2=0
x⁻¹/³=1/3
x¹/³=3
x=27
we have to calculate de second derived
y´´=-2x^(-4/3)
y´´(27)=-0.024<0 ⇒ at x=27 exist a maximum
we calculate y
y=32
Answer: we have a maximum at (27,32)
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f(x)=20+300x
Also, Rex should find a different pool because that fee is ridiculous.
Final answer:
The function rule in the given situation is a linear function and can be represented as C=20+300x. In this rule, 'C' is the total cost in dollars, '20' is the initial membership fee, '300' is the cost of each pool visit and 'x' is the number of pool visits.
Explanation:
The function rule in this situation is called a linear function. A function rule describes how to convert an input (in this case, the number of times Rex visits the pool) into an output (the total cost).
The function rule for this specific situation could be represented as C=20+300x, where 'C' is the total cost, '20' is the initial membership fee, '300' is the cost each time Rex goes to the couple, and 'x' is the number of times Rex goes to the pool.
So, each time Rex goes to the pool, you would multiply that number by 300 (the cost per visit), and then add 20 (the initial fee) to get the total cost.
Learn more about Function Rule here:
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