Complex Operations
1. Evaluate the following complex number operations:
i) \((2 + 3i) + (7 - 2i)\)
Step 1: Add the real parts and the imaginary parts separately.
$$2 + 7 = 9$$
$$3i - 2i = i$$
Step 2: Combine the results:
$$9 + i$$
\(\therefore (2 + 3i) + (7 - 2i) = 9 + i\)
ii) \((3 + 2i) - (7 + 3i)\)
Step 1: Subtract the real parts and the imaginary parts separately.
$$3 - 7 = -4$$
$$2i - 3i = -i$$
Step 2: Combine the results:
$$-4 - i$$
\(\therefore (3 + 2i) - (7 + 3i) = -4 - i\)
2. Find the value of \(\frac{z_1 - z_2}{z_1 + z_2}\) where \(z_1 = -2 + i\) and \(z_2 = 1 - 2i\).
Step 1: Compute \(z_1 - z_2\):
$$(-2 + i) - (1 - 2i) = -2 + i - 1 + 2i = -3 + 3i$$
Step 2: Compute \(z_1 + z_2\):
$$(-2 + i) + (1 - 2i) = -2 + i + 1 - 2i = -1 - i$$
Step 3: Write the expression:
$$\frac{-3 + 3i}{-1 - i}$$
Step 4: Multiply numerator and denominator by the conjugate of the denominator \(-1 + i\) to simplify:
$$\frac{(-3 + 3i)(-1 + i)}{(-1 - i)(-1 + i)}$$
Step 5: Expand the numerator:
$$(-3)(-1) + (-3)(i) + (3i)(-1) + (3i)(i) = 3 - 3i - 3i + 3i^2$$
Knowing \(i^2 = -1\), this becomes:
$$3 - 3i - 3i - 3 = -6i$$
Step 6: Expand the denominator:
$$(-1)^2 - (i)^2 = 1 - (-1) = 2$$
Step 7: Combine:
$$\frac{-6i}{2} = -3i$$
\(\therefore \frac{z_1 - z_2}{z_1 + z_2} = -3i\)