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WAEC 2019 · Paper 1 · Q10

Evaluate 228−350+722\sqrt{28} - 3\sqrt{50} + \sqrt{72}.

Worked solution (try it first)
  1. Take out square factors: 228=2×272\sqrt{28} = 2 \times 2\sqrt7, which is 474\sqrt7.
  2. Likewise 350=3×52=1523\sqrt{50} = 3 \times 5\sqrt2 = 15\sqrt2 and 72=62\sqrt{72} = 6\sqrt2.
  3. Combine the 2\sqrt2 terms: −152+62=−92-15\sqrt2 + 6\sqrt2 = -9\sqrt2.
  4. So the value is 47−924\sqrt7 - 9\sqrt2, option C.

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