Equations practice

Working with the discriminant worksheets

Calculate the discriminant for twelve quadratic equations, then use its sign and square status to count and classify distinct roots. Choose monic, signed nonmonic or mixed leading coefficients.

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Move every term to the left and identify a, b and c without reducing the equation. Calculate D from those displayed coefficients, then follow the section instruction.

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Calculate D before predicting the roots

Each prompt puts the quadratic term on the left and the linear and constant terms on the right. Move them to standard form, retain their signs and calculate D = b² − 4ac from the unreduced coefficients.

A negative D gives two distinct nonreal complex roots. Zero gives one distinct repeated rational root. A positive perfect square gives two distinct rational roots; a positive nonsquare gives two distinct irrational real roots. Every section includes all four cases.

Learning objective

What this activity builds

Identify the standard-form coefficients and use D = b² − 4ac to predict the number and type of distinct roots.

Worked example

For 5k² = −15k + 10, calculate D and classify the roots.

D = 425; two distinct irrational real roots.

Move the terms left: 5k² + 15k − 10 = 0, so a = 5, b = 15 and c = −10. D = 15² − 4(5)(−10) = 425. It is positive and not a perfect square.

Teaching notes

Make the practice count

  • Move every term before identifying the coefficients.
  • Keep the signs of b and c when substituting.
  • Use the displayed coefficients even when they share a common factor.
  • Interpret D = 0 as one distinct repeated rational root.
  • Distinguish nonreal complex roots from purely imaginary numbers.

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Each twelve-question sheet has three four-question sections and includes negative, zero, positive-square and positive-nonsquare discriminants in every section.

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Math SheetNameScore/ 12TeacherDateWorking with the DiscriminantUse D = b² - 4ac for the equation after moving every term to the left. Follow the instruction for each section.1–4 Calculate the discriminant1.m² = 4m - 312.b² = -4b - 43.n² = 10n - 104.y² = -20y - 195–8 Calculate D and count the distinct real or nonreal complex roots5.z² = -18z + 406.a² = -2a - 17.c² = 22c - 238.s² = -7s - 269–12 Calculate D and classify the distinct roots9.x² = 30x - 1110.r² = 8r - 1611.p² = -4p + 3212.q² = 11q - 32math-sheet.comPage 1 / 1

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