Question Details

If x + 1 x = 2 , then find the value of ( x 4 + 4 ( x ) 4 ) ( x 3 4 x 3 ) .

Options

A

−10

B

10

C

−15

D

15

Show Answer

Correct Answer :

Option B

10

Solution :

The correct option/answer is -15. Note: While solving the equation x+1x=2 gives x=1, substituting x=1 into the target expression yields:
( x 4 + 4 x 4 ) ( x 3 4 x 3 ) = ( 1 + 4 ) ( 1 4 ) = 5 × ( 3 ) = 15 .

Let us break down the solution step-by-step:

Step 1: Solve the given equation for x
We are given the equation:
x + 1 x = 2
Multiply both sides of the equation by x to eliminate the fraction:
x 2 + 1 = 2 x
Rearranging the terms gives a quadratic equation:
x 2 2 x + 1 = 0
This quadratic equation can be factored as a perfect square:
( x 1 ) 2 = 0
Taking the square root of both sides, we find:
x = 1

Step 2: Substitute x = 1 into the expression
Now we substitute x=1 into the expression we need to evaluate:
( x 4 + 4 x 4 ) ( x 3 4 x 3 )
Evaluating the first factor:
1 4 + 4 1 4 = 1 + 4 = 5
Evaluating the second factor:
1 3 4 1 3 = 1 4 = 3
Multiply the two results:
5 × ( 3 ) = 15

Therefore, the value of the expression is -15.

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