Questions
Question 1
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What point in the complex plane represents \(4-3i\)?
Question 2
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State the vector rule for adding \(z_1=a_1+b_1i\) and \(z_2=a_2+b_2i\).
Question 3
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Find the vector represented by \((2+i)+(3+4i)\).
Question 4
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Which complex number represents the vector from the origin to \((-1,6)\)?
Question 5
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Add \(-2+5i\) and \(7-3i\), and describe the geometric operation.
Question 6
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Find \((1-4i)-(6+i)\) and interpret it as a displacement.
Question 7
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If \(z_1=3+2i\) and \(z_1+z_2=-1+5i\), find \(z_2\).
Question 8
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Find the fourth vertex of the parallelogram with adjacent vertices \(0\), \(2+i\), and \(-1+4i\).
Question 9
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Let \(z_1=4+i\) and \(z_2=-2+3i\). Verify the triangle inequality for this pair.
Question 10
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Find the midpoint of the segment joining \(3-5i\) and \(-1+i\) in complex form.
Question 11
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Explain why \(z_1-z_2\) represents the vector from \(z_2\) to \(z_1\).
Question 12
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A student says \(|z_1+z_2|=|z_1|+|z_2|\) for all complex numbers. Give a counterexample and explain it geometrically.
Question 13
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The points \(0\), \(z\), \(w\), and \(z+w\) form a parallelogram. For \(z=2-3i\) and \(w=-5+i\), find both diagonals as complex displacements.
Question 14
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Find \(z\) if the parallelogram with vertices \(0\), \(2+i\), \(z\), and \(5-2i\) has \(5-2i\) as the vertex opposite \(0\).
Question 15
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For which real \(t\) are \(2+ti\) and \(-4-2ti\) opposite vectors?
Question 16
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For which real \(t\) is the sum \((t+2i)+(3-ti)\) purely real?
Question 17
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For which real \(t\) is the displacement from \(1+ti\) to \(4-2i\) horizontal?
Question 18
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Prove the parallelogram identity \(|z+w|^2+|z-w|^2=2|z|^2+2|w|^2\) for \(z=a+bi\), \(w=c+di\).
Question 19
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Show that equality in \(|z+w|\le |z|+|w|\) holds for \(z=2(1+i)\) and \(w=5(1+i)\), and explain why.
Question 20
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A learner claims that if \(|z+w|=|z-w|\), then \(z=0\) or \(w=0\). Disprove the claim geometrically with a complex example.