Stepwise
Start practisingPractise

WAEC 2024 · Paper 1 · Q6

If (3−42)(1+32)=a+b2(3 - 4\sqrt2)(1 + 3\sqrt2) = a + b\sqrt2, find the value of bb.

Worked solution (try it first)
  1. Multiply out each pair: 3×1=33 \times 1 = 3, 3×32=923 \times 3\sqrt2 = 9\sqrt2, −42×1=−42-4\sqrt2 \times 1 = -4\sqrt2 and −42×32=−24-4\sqrt2 \times 3\sqrt2 = -24.
  2. Collect the whole numbers: 3−24=−213 - 24 = -21.
  3. Collect the surds: 92−42=529\sqrt2 - 4\sqrt2 = 5\sqrt2.
  4. So the product is −21+52-21 + 5\sqrt2, and b=5b = 5, option A.

Report a problem with this question