Problem 1
- Test level
- Multiple choice
- No calculator
- 4 pts
Which number equals ?
Answer
Multiply numerator and denominator by the conjugate. The denominator becomes , so the reciprocal is .
Full solution
The conjugate of the denominator is .
The product of a number and its conjugate is , a positive real number.
Split the resulting numerator into real and imaginary parts. The imaginary part keeps a minus sign from .
Where students lose points
The conjugate itself is not the reciprocal unless the modulus equals .

