Here are the solutions to the questions from the image.
Question 1 (i)
Given the expression P(x)=ax3+bxβa.
Since (x+1) and (xβ2) are factors, by the Factor Theorem, P(β1)=0 and P(2)=0.
Step 1: Use P(β1)=0 to form an equation.
P(β1)=a(β1)3+b(β1)βa=βaβbβa=β2aβb
Setting P(β1)=0:
β2aβb=0βΉ2a+b=0(1)
Step 2: Use P(2)=0 to form another equation.
P(2)=a(2)3+b(2)βa=8a+2bβa=7a+2b
Setting P(2)=0:
7a+2b=0(2)
Step 3: Solve the system of equations for a and b.
From equation (1), we can express b in terms of a:
b=β2a
Substitute this into equation (2):
7a+2(β2a)=0
7aβ4a=0
3a=0
a=0
Now substitute a=0 back into b=β2a:
b=β2(0)=0
So, the values of the constants are a=0 and b=0.
Step 4: Find the remainder when the expression is divided by (xβ1).
The expression is P(x)=ax3+bxβa. With a=0 and b=0, the expression becomes P(x)=0.
By the Remainder Theorem, the remainder when P(x) is divided by (xβ1) is P(1).
P(1)=a(1)3+b(1)βa=a+bβa=b
Since b=0, the remainder is 0.
The values of the constants are a=0,b=0β and the remainder is 0β.
Question 1 (ii)
Express as a single fraction x2+2xβ35β, simplifying the numerator.
Step 1: Factor the denominator.
We need to find two numbers that multiply to β3 and add to 2. These numbers are 3 and β1.
So, x2+2xβ3=(x+3)(xβ1).
Step 2: Write the fraction with the factored denominator.
(x+3)(xβ1)5β
The numerator is already simplified as it is a constant 5. The expression is already a single fraction.
The simplified form of the fraction is (x+3)(xβ1)5ββ.
Question 6 (i)
The functions f and g are defined by f(x)=xβ23β, xβR,xξ =2, and g(x)=x+2xβ1β, xβR,xξ =β2.
(a) Find fg(x) and gf(x), stating their domains.
Step 1: Find fg(x).
fg(x)=f(g(x))=f(x+2xβ1β).
Substitute g(x) into f(x):
fg(x)=(x+2xβ1β)β23β
Simplify the denominator:
x+2xβ1ββ2=x+2xβ1ββx+22(x+2)β=x+2xβ1β2xβ4β=x+2βxβ5β
So,
fg(x)=x+2βxβ5β3β=β(x+5)3(x+2)β=βx+53(x+2)β
Step 2: Determine the domain of fg(x).
The domain of fg(x) requires two conditions:
- x must be in the domain of g(x), so xξ =β2.
- g(x) must be in the domain of f(x), so g(x)ξ =2.
x+2xβ1βξ =2
xβ1ξ =2(x+2)
xβ1ξ =2x+4
β5ξ =x
Combining these, the domain of fg(x) is xβR,xξ =β2,xξ =β5.
fg(x) = -\frac{3(x+2){x+5}, Domain: \{x \in \mathbb{R} \mid x \neq -2, x \neq -5\}}
Step 3: Find gf(x).
gf(x)=g(f(x))=g(xβ23β).
Substitute f(x) into g(x):
gf(x)=(xβ23β)+2(xβ23β)β1β
Simplify the numerator:
xβ23ββ1=xβ23β(xβ2)β=xβ25βxβ
Simplify the denominator:
xβ23β+2=xβ23+2(xβ2)β=xβ23+2xβ4β=xβ22xβ1β
So,
gf(x)=xβ22xβ1βxβ25βxββ=2xβ15βxβ
Step 4: Determine the domain of gf(x).
The domain of gf(x) requires two conditions:
- x must be in the domain of f(x), so xξ =2.
- f(x) must be in the domain of g(x), so f(x)ξ =β2.
xβ23βξ =β2
3ξ =β2(xβ2)
3ξ =β2x+4
2xξ =1
xξ =21β
Combining these, the domain of gf(x) is xβR,xξ =2,xξ =21β.
gf(x) = \frac{5-x{2x-1}, Domain: \{x \in \mathbb{R} \mid x \neq 2, x \neq \frac{1}{2}\}}
(b) Show that g is not surjective.
Step 1: Understand surjectivity.
A function g:AβB is surjective if for every element y in the codomain B, there exists at least one element x in the domain A such that g(x)=y.
The function g(x)=x+2xβ1β has a domain of Rβ{β2}. Assuming the codomain is R.
Step 2: Try to express x in terms of y.
Let y=g(x).
y=x+2xβ1β
Multiply both sides by (x+2):
y(x+2)=xβ1
yx+2y=xβ1
Rearrange to solve for x:
2y+1=xβyx
2y+1=x(1βy)
x=1βy2y+1β
Step 3: Identify values of y for which x does not exist.
For x to be defined, the denominator 1βy cannot be zero.
1βyξ =0βΉyξ =1
This means that there is no value of x in the domain of g that can produce y=1. In other words, 1 is not in the range of g.
Since the codomain of g is R (which includes 1), and the range of g does not include all values in the codomain (specifically, it does not include 1), the function g is not surjective.
SinceΒ y=1Β isΒ notΒ inΒ theΒ rangeΒ ofΒ g(x),Β gΒ isΒ notΒ surjective.
Question 6 (ii)
A relation R is defined on the set A={1,2,3,4,5} by aRbβΊa+b=2n,nβN. List all the equivalence classes of A under R.
Step 1: Understand the relation aRb.
The condition a+b=2n means that the sum a+b must be an even number. This occurs if and only if a and b have the same parity (both even or both odd).
Step 2: Identify elements in set A by parity.
Odd numbers in A: {1,3,5}
Even numbers in A: {2,4}
Step 3: Determine the equivalence classes.
An equivalence class [a] consists of all elements xβA such that aRx.
For a=1:
[1]={xβAβ£1Rx}. This means 1+x must be even, so x must be odd.
The odd numbers in A are {1,3,5}.
So, [1]={1,3,5}.
For a=2:
[2]={xβAβ£2Rx}. This means 2+x must be even, so x must be even.
The even numbers in A are {2,4}.
So, [2]={2,4}.
For a=3:
[3]={xβAβ£3Rx}. This means 3+x must be even, so x must be odd.
So, [3]={1,3,5}. This is the same as [1].
For a=4:
[4]={xβAβ£4Rx}. This means 4+x must be even, so x must be even.
So, [4]={2,4}. This is the same as [2].
For a=5:
[5]={xβAβ£5Rx}. This means 5+x must be even, so x must be odd.
So, [5]={1,3,5}. This is the same as [1].
The distinct equivalence classes are the sets of numbers with the same parity.
The equivalence classes of A under R are {1,3,5}and{2,4}β.
Question 7 (i)
This question was solved in a previous turn. The solution was ΞΈ=6Οβ,2Οβ,65Οβ,23Οββ.
Question 7 (ii)
This question was solved in a previous turn. The solution was Sincedet(M)=β41ξ =0,thematrixMisinvertible.β.
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