Given the polynomial function:
f(x)=ax3+bx2+cx+41
We are provided the following conditions from the problem:
1. f(1)=40
2. f′(1)=2
3. f′′(1)=4
First, calculate f(1) :
f(1)=a(1)3+b(1)2+c(1)+41=40
Simplifying, we get:
a+b+c+41=40
Therefore:
a+b+c=−1
Next, calculate the first derivative f′(x) :
f′(x)=3ax2+2bx+c
Given f′(1)=2 :
f′(1)=3a(1)2+2b(1)+c=2
Simplifying, we get:
3a+2b+c=2
Next, calculate the second derivative f′′(x) :
f′′(x)=6ax+2b
Given f′′(1)=4 :
f′′(1)=6a(1)+2b=4
Simplifying, we get:
6a+2b=4
Dividing the entire equation by 2:
3a+b=2
We now have three equations:
1. a+b+c=−1
2. 3a+2b+c=2
3. 3a+b=2
To solve for a , b , and c , follow these steps:
First, subtract the third equation from the second equation:
(3a+2b+c)−(3a+b)=2−2
Which simplifies to:
b+c=0
So,
c=−b
Substitute c=−b into the first equation:
(a+b−b=−1)
Simplifying, we get:
a=−1
Now substitute a=−1 into the third equation:
3(−1)+b=2
Which simplifies to:
−3+b=2
Therefore:
b=5
Next, since c=−b :
c=−5
Finally, we need to find a2+b2+c2 :
a2+b2+c2=(−1)2+52+(−5)2
Simplifying, we get:
1+25+25=51
Therefore, the answer is:
Option B: 51