Question Details

If 9 x2 + 2x 3 4 ( 3 x2 + 2x 2 ) + 27 = 0   then the product of all possible values of x is

Options

A

30

B

20

C

5

D

15

Show Answer

Correct Answer :

Option B

20

Solution :

The correct option is 20.

We are given the exponential equation:

9 x2 + 2x 3 4 ( 3 x2 + 2x 2 ) + 27 = 0

Step 1: Simplify the exponential terms
Let y = x2 + 2x .
Substitute y into the exponent terms:

9 y 3 4 ( 3 y 2 ) + 27 = 0

Rewrite base 9 as 32 :

( 32 ) y 3 4 ( 3 y 2 ) + 27 = 0

3 2y 6 4 ( 3 y 2 ) + 27 = 0

Multiply the entire equation by 36 to clear denominators, or express in terms of t = 3y :

32y 36 4 3y 32 + 27 = 0

Substitute t = 3y (where t > 0):

t2 729 4t 9 + 27 = 0

Multiply the entire equation by 729:

t2 4 81t + 27 729 = 0

t2 324t + 19683 = 0

Step 2: Solve the quadratic equation for t
We look for factors of 19683 that sum to 324:
Notice that 81 + 243 = 324 and 81 × 243 = 34 × 35 = 39 = 19683 .

So the equation factors as:

( t 81 ) ( t 243 ) = 0

Thus, the roots for t are:

t = 81 = 34 or t = 243 = 35

Step 3: Solve for y
Since t = 3y :

1. If 3y = 34 , then y = 4
2. If 3y = 35 , then y = 5

Step 4: Solve for x
Recall that y = x2 + 2x .

Case 1: x2 + 2x = 4

x2 + 2x 4 = 0

Let the roots of this equation be x1 and x2 . By Vieta's formulas, the product of roots is:

x1 x2 = 4

Case 2: x2 + 2x = 5

x2 + 2x 5 = 0

Let the roots of this equation be x3 and x4 . By Vieta's formulas, the product of roots is:

x3 x4 = 5

Step 5: Find the product of all possible values of x
The product of all four real solutions x1, x2, x3, and x4 is:

Product = ( x1 x2 ) ( x3 x4 ) = (4) (5) = 20

Thus, the product of all possible values of x is 20.

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