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Cube Roots
Evaluate without a calculator: (5 sqrt2 + 7)^{1/3} - (5 sqrt2 - 7)^1/3}.
Conjugate Tracker
Stage: 5
Challenge Level:
This Hint is for students who have only recently met complex numbers.
What can you say about the product of the roots of the quadratic equation $x^2 + px + q = 0$?
If the roots of this quadratic equation, where $p$ and $q$ are real coefficients, are the complex numbers $z_1$ and $z_2$ explain why $z_1$ and $z_2$ are complex conjugates.
Explain why the square of the distance from the origin of the point $u+iv$ in the Argand diagram is given by the product of complex conjugates $(u+iv)(u-iv)$.
What does this tell you about the locus of the complex roots of $x^2 +px +q = 0$ as you change $p$ keeping $q$ constant?
Was your conjecture correct?
Generalising
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Making and proving conjectures
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Argand diagram
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Surds
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Golden ratio
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Quadratic equations
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Complex roots of equations in conjugate pairs
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Complex numbers
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Mathematical reasoning & proof
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Interactivities
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