Explanation
Step 1: Calculate the divided differences.
We'll calculate the divided differences using the given data:
-
ΔF[0] = F(1) - F(0) = 14 - 1 = 13
-
ΔF[1] = F(2) - F(1) = 2 - 14 = -12
-
ΔF[2] = F(3) - F(2) = 15 - 2 = 13
-
ΔF[3] = F(4) - F(3) = 4 - 15 = -11
-
ΔF[4] = F(5) - F(4) = 5 - 4 = 1
-
ΔF[5] = F(6) - F(5) = 6 - 5 = 1
-
ΔF[6] = F(7) - F(6) = 19 - 6 = 13
Step 2: Calculate the interpolating polynomial.
The Lagrange interpolating polynomial is given by:
P(x) = F(x0) + (x - x0)ΔF[0] + (x - x0)(x - x1)ΔF[0,1] + ...
Here, x0 = 2, x1 = 1, and ΔF[0] = 13. So, the interpolating polynomial is:
P(x) = 14 + (x - 2)ΔF[0] - (x - 2)(x - 1)ΔF[0,1]
Now, we need to calculate ΔF[0,1]:
ΔF[0,1] = (ΔF[1] - ΔF[0]) / (x1 - x0) = (-12 - 13) / (1 - 2) = 25
So, the interpolating polynomial becomes:
P(x) = 14 + (x - 2)13 - (x - 2)(x - 1)25
Step 3: Evaluate P(3) to find F(3):
P(3) = 14 + (3 - 2)13 - (3 - 2)(3 - 1)25 P(3) = 14 + 13 - 2 * 25 P(3) = 14 + 13 - 50 P(3) = 27 - 50 P(3) = -23
So, F(3) is approximately equal to -23.
Step 1: Calculate the divided differences.
We'll calculate the divided differences using the given data. The divided difference table is as follows:
x |
F(x) |
Δ0 |
Δ1 |
Δ2 |
Δ3 |
Δ4 |
Δ5 |
Δ6 |
0 |
1 |
|
|
|
|
|
|
|
1 |
14 |
13 |
|
|
|
|
|
|
2 |
2 |
-12 |
-25 |
|
|
|
|
|
3 |
15 |
13 |
25 |
26 |
|
|
|
|
4 |
4 |
-11 |
14 |
18 |
16 |
|
|
|
5 |
5 |
1 |
12 |
16 |
16 |
15 |
|
|
6 |
6 |
1 |
2 |
4 |
-2 |
0 |
0 |
|
7 |
19 |
13 |
12 |
10 |
4 |
4 |
4 |
4 |
Step 2: Calculate the interpolating polynomial.
The Lagrange interpolating polynomial is given by:
(x)=F(x0)+(x−x0)Δ0+(x−x0)(x−x1)Δ0,1+(x−x0)(x−x1)(x−x2)Δ0,1,2+...+(x−x0)(x−x1)...(x−xn−1)Δ0,1,...,n−1
Here, 0x0=0, 1x1=1, 2x2=2, 3x3=3, and we have already calculated the divided differences. So, the interpolating polynomial is:
(x)=1+xΔ0+x(x−1)Δ0,1+x(x−1)(x−2)Δ0,1,2+x(x−1)(x−2)(x−3)Δ0,1,2,3
Now, we need to substitute the values for Δ0, Δ0,1, Δ0,1,2, and Δ0,1,2,3:
Δ0 = 13 Δ0,1 = 25 Δ0,1,2 = 26 Δ0,1,2,3 = 4
So, the interpolating polynomial becomes:
P(x)=1+13x+25x(x−1)+26x(x−1)(x−2)+4x(x−1)(x−2)(x−3)
Step 3: Evaluate P(3) to find F(3):
p(3)=1+13(3)+25(3)(3−1)+26(3)(3−1)(3−2)+4(3)(3−1)(3−2)(3−3)P(3)=1+13(3)+25(3)(3−1)+26(3)(3−1)(3−2)+4(3)(3−1)(3−2)(3−3)
p(3)=1+39+150+78+0P(3)=1+39+150+78+0
p(3)=268
So F(3)=268.