Exponents and radicals practice

Logarithmic equations worksheets

Solve six types of logarithmic equations with exact answers. Choose 12, 14 or 16 questions and check every solution in the original logarithms.

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Solve each equation over the real numbers. Give exact answers and check that every original logarithm has a positive argument.

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Check every candidate in the original equation

Choose any of six equation forms and 12, 14 or 16 questions. Use equal arguments or logarithm laws to obtain a linear or quadratic equation. Answers stay exact, including simplified square roots.

Every original logarithm must have a positive argument. The answer key checks each candidate and explains which values are excluded. A negative candidate can still be valid; test the argument rather than the sign of the variable alone.

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Learning objective

What this activity builds

Use logarithm laws to solve linear and quadratic equations, then reject candidates outside the original domain.

Worked example

Solve log base 2 of (3x squared - 60) = log base 2 of (3x).

The algebraic candidates are -4 and 5. Only x = 5 is a solution.

Equal logarithms with the same base have equal positive arguments. Set 3x squared - 60 = 3x, then factor x squared - x - 20. At x = -4 both arguments are -12, so discard it. At x = 5 both arguments are 15.

Teaching notes

Make the practice count

  • Write the original argument restrictions before simplifying.
  • Combine a sum of logarithms using the product rule.
  • Keep irrational answers as simplified square roots.
  • A negative candidate can be valid when every original argument is positive.

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Choose equation forms and worksheet length. Keep exact answers and check the original logarithm arguments.

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Math SheetNameScore/ 12TeacherDateLogarithmic EquationsUse logarithm laws, solve the resulting equation, and check every candidate in the original logarithms.1.log9y+log97log98Domain: real variablesy02.log8z+log8102Domain: real variablesz03.log52+log54·z2log52Domain: real variables4·z20math-sheet.comPage 1 / 4
Math SheetNameScore/ 12TeacherDateLogarithmic EquationsUse logarithm laws, solve the resulting equation, and check every candidate in the original logarithms.4.log37·n2+21log328·nDomain: real variables7·n2+21028·n05.log73·nlog72·n+5Domain: real variables3·n02·n+506.log49·z-9log48·z-4Domain: real variables9·z-908·z-407.log89·n+5log86·n-7Domain: real variables9·n+506·n-70math-sheet.comPage 2 / 4
Math SheetNameScore/ 12TeacherDateLogarithmic EquationsUse logarithm laws, solve the resulting equation, and check every candidate in the original logarithms.8.log6z+log610log610Domain: real variablesz09.log92+log92·t2log92Domain: real variables2·t2010.log39·x2+18log3-27·xDomain: real variables9·x2+180-27·x0math-sheet.comPage 3 / 4
Math SheetNameScore/ 12TeacherDateLogarithmic EquationsUse logarithm laws, solve the resulting equation, and check every candidate in the original logarithms.11.log4z+log492Domain: real variablesz012.log34·nlog35·n+6Domain: real variables4·n05·n+60math-sheet.comPage 4 / 4

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