Question Details

How many distinct positive integer-valued solutions exist to the equation (x2-7x+11)x2-13x+42=1?

Options

A

6

B

8

C

2

D

4

Show Answer

Correct Answer :

Option A

6

Solution :

For an equation of the form AB=1, there are three possible cases:

Case 1: The exponent is zero and the base is non-zero.
x213x+42=0
(x6)(x7)=0
This gives x=6 and x=7.
Checking the base for these values:
For x=6: 627(6)+11=3642+11=50.
For x=7: 727(7)+11=110.
So, x=6,7 are valid positive integer solutions.

Case 2: The base is equal to 1.
x27x+11=1
x27x+10=0
(x2)(x5)=0
This gives x=2 and x=5.
Since these are positive integers, they are valid solutions.

Case 3: The base is equal to -1 and the exponent is an even integer.
x27x+11=1
x27x+12=0
(x3)(x4)=0
This gives x=3 and x=4.
Checking if the exponent is even for these values:
For x=3: Exponent = 3213(3)+42=939+42=12 (even).
For x=4: Exponent = 4213(4)+42=1652+42=6 (even).
So, x=3,4 are also valid positive integer solutions.

Summarizing all valid solutions: x{2,3,4,5,6,7}.
Thus, there are 6 distinct positive integer solutions.

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