Evaluate the Function for the Given Values of x :
Here we are going to see some example problems to understand evaluating the functions for the given values of x.
Question 1 :
Given the function f : x -> x2 −5x + 6 , evaluate
(i) f (-1)
(ii) f (2a)
(iii) f (2)
(iv) f (x −1)
Solution :
Given that :
f(x) = x2 −5x + 6
(i) f (-1)
here we have -1 instead of x.
f(-1) = (-1)2 −5(-1) + 6
= 1 + 5 + 6
f(-1) = 12
(ii) f (2a)
here we have 2a instead of x.
f(2a) = (2a)2 −5(2a) + 6
= 4a2 - 10a + 6
(iii) f (2)
here we have 2 instead of x.
f(2) = (2)2 −5(2) + 6
= 4 - 10 + 6
= 0
(iv) f (x −1)
here we have x - 1 instead of x.
f(x-1) = (x-1)2 −5(x-1) + 6
= x2 - 2x + 1 - 5x + 5 + 6
= x2 - 7x + 12
Question 2 :
A graph representing the function f (x) is given figure
it is clear that f (9) = 2.
(i) Find the following values of the function
(a) f (0) (b) f (7) (c) f (2) (d) f (10)
(ii) For what value of x is f (x) = 1?
(iii) Describe the following (i) Domain (ii) Range.
(iv) What is the image of 6 under f ?
Solution :
(i)
(a) f(0) = 9, (b) f(7) = 6, (c) f (2) = 6, (d) f (10) = 0
(ii) For what value of x is f (x) = 1 ?
For x = 9.5, we get 1.
(iii) Describe the following (i) Domain (ii) Range.
Domain = { 0 ≤ x ≤ 10 }
Range = { 0 ≤ x ≤ 9 }
(iv) What is the image of 6 under f ?
Question 3 :
Let f (x) = 2x + 5. If x ≠ 0 then find [f(x + 2) - f(2)] / x
Solution :
f (x) = 2x + 5
f(x + 2) = 2(x + 2) + 5
f(x + 2) = 2x + 4 + 5 -------(1)
f(x + 2) = 2x + 9
f(2) = 2(2) + 5
= 4 + 5
f(2) = 9 -------(2)
(1) - (2) = 2x + 9 - 9
= 2x
[f(x + 2) - f(2) ]/x = 2x / x = 2
Question 4 :
A function f is defined by f (x) = 2x – 3
(i) find [f(0) + f(1)]/2
(ii) find x such that f (x) = 0.
(iii) find x such that f (x) = x .
(iv) find x such that f (x) = f (1−x) .
Solution :
f(x) = 2x – 3
(i) [f(0) + f(1)]/2
f(0) = 2(0) - 3 = -3
f(1) = 2(1) - 3 = -1
[f(0) + f(1)]/2 = [-3 + (-1)] / 2
= -4/2
= -2
Hence the answer is -2.
(ii) find x such that f (x) = 0.
f(x) = 2x – 3
2x - 3 = 0
2x = 3
x = 3/2
Hence the answer is 3/2.
(iii) find x such that f (x) = x .
f(x) = 2x – 3
2x - 3 = x
2x - x = 3
x = 3
Hence the answer is 3
(iv) find x such that f (x) = f (1−x) .
f(1 - x) = 2(1- x) - 3
= 2 - 2x - 3
= -2x - 1
2x - 3 = -2x - 1
2x + 2x = - 1 + 3
4x = 2
x = 2/4 = 1/2
Hence the answer is 1/2.
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