1. Form two equations using the points $(-2, 1)$ and $(2, -3)$ on the graph of $y = \mathrm{f}(x)$.
Since the graph of y=f(x) passes through (−2,1) and (2,−3), we have f(−2)=1 and f(2)=−3.
(−2)3+a(−2)2+b(−2)+c=1
−8+4a−2b+c=1
4a−2b+c=9— (1)
(2)3+a(2)2+b(2)+c=−3
8+4a+2b+c=−3
4a+2b+c=−11— (2)
2. Form a third equation using the point $(2, 1)$ on the graph of $y = \mathrm{f}(x + 1)$.
The point (2,1) lies on y=f(x+1), so substituting x=2 and y=1 yields:
1=f(2+1)⟹f(3)=1
Substituting x=3 into f(x):
33+a(3)2+b(3)+c=1
27+9a+3b+c=1
9a+3b+c=−26— (3)
3. Solve the system of three linear equations to find $a$, $b$, and $c$.
Subtracting (1) from (2):
(4a+2b+c)−(4a−2b+c)=−11−9
4b=−20⟹b=−5
Substituting b=−5 into (1) and (3):
4a−2(−5)+c=9⟹4a+c=−1— (4)
9a+3(−5)+c=−26⟹9a+c=−11— (5)
Subtracting (4) from (5):
(9a+c)−(4a+c)=−11−(−1)
5a=−10⟹a=−2
Substituting a=−2 into (4):
4(−2)+c=−1⟹−8+c=−1⟹c=7
(Note: The system can also be solved directly using a graphing calculator.)
答案a=−2, b=−5, c=7