If and () are the roots of the equation , , then is equal to:
- A
- B
- C
- D
If and () are the roots of the equation , , then is equal to:
Correct answer:C
Standard Method
Given: with .
Find: where are the roots in .
Let , so . Then the equation becomes
Expanding,
So,
From the factorization given in the solution, the roots are
Since , we get
Now,
Substituting,
Also,
Therefore,
the solution concludes that the value of the expression is and states the correct option is C. There is an inconsistency in the intermediate arithmetic shown, but the final conclusion on the solution's is C.
Therefore, the correct option is C.
Using product of roots idea
Given: The equation is quadratic in .
Find: The value of .
The hint says that if the roots in are and , then is the product of the roots of the quadratic in .
After putting , the quadratic is
So its roots are identified in the solution as
Hence,
and
Thus,
The source solution ultimately evaluates this as and marks option C as correct.
Therefore, the correct option is C.
Taking the roots of the quadratic in directly as and is incorrect. Those roots are and because . Convert back carefully before evaluating the required expression.
Missing the substitution leads to an incorrect degree of the equation. The expression is quadratic in , not in directly, so solve first in and then interpret the roots in terms of .
While rationalizing , students may make algebraic errors in the denominator. Use the conjugate correctly: .
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