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Topic summary · Pure advanced (P4)

Partial Fractions summary

Partial fractions decompose rational functions into simpler pieces for integration or series work.

Files: P4-Partial Fractions.pdf · P4-Partial Fractions answers.pdf · free public downloads · diagrams in the PDFs

Key learning points

  • Linear factors → Ax−a\frac{A}{x-a}; repeated → include B(x−a)2\frac{B}{(x-a)^2}.
  • Irreducible quadratics get a linear numerator.
  • Equate coefficients or substitute convenient xx values.
  • Divide first if the fraction is improper.

Worked example 1 — Equivalent fractions

Write three fractions equivalent to 25\tfrac{2}{5}.

Working

410, 615, 820\tfrac{4}{10},\ \tfrac{6}{15},\ \tfrac{8}{20}

Multiply numerator and denominator by the same integer.

Worked example 2 — Simplifying

Simplify 1620\tfrac{16}{20}.

Working

16÷420÷4=45\tfrac{16\div4}{20\div4}=\tfrac{4}{5}

Divide by the HCF of 16 and 20, which is 4.

Worked example 3 — Addition

Calculate 23+14\tfrac{2}{3}+\tfrac{1}{4}.

Working

812+312=1112\tfrac{8}{12}+\tfrac{3}{12}=\tfrac{11}{12}

LCD of 3 and 4 is 12.

Worked example 4 — Subtraction

Calculate 56−14\tfrac{5}{6}-\tfrac{1}{4}.

Working

1012−312=712\tfrac{10}{12}-\tfrac{3}{12}=\tfrac{7}{12}

LCD of 6 and 4 is 12.

Worked example 5 — Multiplication

Calculate 25×34\tfrac{2}{5}\times\tfrac{3}{4}.

Working

2×35×4=620=310\tfrac{2\times3}{5\times4}=\tfrac{6}{20}=\tfrac{3}{10}

Multiply numerators and denominators, then simplify.

Worked example 6 — Division

Calculate 34÷25\tfrac{3}{4}\div\tfrac{2}{5}.

Working

34×52=158=178\tfrac{3}{4}\times\tfrac{5}{2}=\tfrac{15}{8}=1\tfrac{7}{8}

Multiply by the reciprocal of the divisor.

Worked example 7 — Mixed numbers

Calculate 112+2131\tfrac{1}{2}+2\tfrac{1}{3}.

Working

32+73=96+146=236=356\tfrac{3}{2}+\tfrac{7}{3}=\tfrac{9}{6}+\tfrac{14}{6}=\tfrac{23}{6}=3\tfrac{5}{6}

Convert to improper fractions before adding.

Worked example 8 — Fraction of an amount

Find 35\tfrac{3}{5} of £40£40.

Working

35×40=24\tfrac{3}{5}\times40=24

Divide by the denominator, then multiply by the numerator.

Worked example 9 — Linear factors

Decompose 5x+3(x+1)(x−1)\frac{5x+3}{(x+1)(x-1)}.

Working

1x+1+4x−1\frac{1}{x+1}+\frac{4}{x-1}

Clear denominators and solve for the constants.

Scaffolded Learning Sheet and answers (PDFs)

This page is a short, searchable overview for revision and search engines. Use the Scaffolded Learning Sheet first, then the Answers PDF for a full written solution. The printable PDFs remain the main classroom resource.