To find the value of p(2), we begin by analyzing the given limit:
limx→0(1+x2p(x))=2
Subtracting 1 from both sides gives:
limx→0x2p(x)=1
Since p(x) is a polynomial of degree 4, we can express it in standard form as:
p(x)=ax4+bx3+cx2+dx+e
For the limit limx→0x2p(x) to exist and be finite, the terms of degree less than 2 must be zero:
e=0andd=0
Furthermore, the coefficient of x2 is given by the value of the limit:
c=1
Thus, the polynomial takes the form:
p(x)=ax4+bx3+x2
Next, we calculate the first derivative of p(x):
p′(x)=4ax3+3bx2+2x
Since p(x) has extrema at x=1 and x=2, we have p′(1)=0 and p′(2)=0:
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For x=1:
p′(1)=4a(1)3+3b(1)2+2(1)=0⟹4a+3b+2=0⟹4a+3b=−2
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For x=2:
p′(2)=4a(2)3+3b(2)2+2(2)=0⟹32a+12b+4=0
Dividing this equation by 4 gives:
8a+3b=−1
Now, subtracting the first equation from the second equation:
(8a+3b)−(4a+3b)=−1−(−2)
4a=1⟹a=41
Substituting a=41 back into 4a+3b=−2:
4(41)+3b=−2⟹1+3b=−2⟹3b=−3⟹b=−1
Therefore, the polynomial is:
p(x)=41x4−x3+x2
Finally, we evaluate p(2):
p(2)=41(2)4−(2)3+(2)2=41(16)−8+4=4−8+4=0