To calculate f(0), we'll substitute x by 0 in the
expression of f(x):
f(0) = m*0^4 + n*0^2
+p
f(0) = p
But f(0) = 4 (from
enunciation) => p = 4
Now, we'll calculate
f'(x):
f'(x) = (mx^4 + nx^2
+p)'
f'(x) = 4mx^3 + 2nx
But
f'(1) = 14
We'll calculate f'(1) substituting x by 1 in the
expression of the first derivative:
f'(1) = 4m*1^3 +
2n*1
f'(1) = 4m + 2n
But f'(1)
= 14 => 4m + 2n = 14
We'll divide by
2:
2m + n = 7
n = 7 – 2m
(1)
Now, we'll calculate the definite
integral:
Int f(x) dx = Int (mx^4 + nx^2 +p)dx = F(1) -
F(0)
Int (mx^4 + nx^2 +p)dx = mInt x^4dx + nInt x^2dx +
pInt dx
Int (mx^4 + nx^2 +p)dx = m*x^5/5 + n*x^3/3 +
px
F(1) = m/5 + n/3 + p
F(0) =
0
But Int f(x)dx = 6 => m/5 + n/3 + p =
6
3m + 5n + 15p = 90
But p =
4=> 3m + 5n = 90 - 60
3m + 5n = 30
(2)
We'll substitute (1) in
(2):
3m + 5(7 – 2m) = 30
3m+
35 – 10m = 30
-7m = -5
m =
5/7
n = 7 – 10/7
n =
39/7
The function f(x) is:
f(x) = (5x^4)/7 + (39x^2)/7 + 4
No comments:
Post a Comment