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WAEC 2019 · Paper 2 · Q2

  1. (a)

    Find the equation of the line which passes through the points A(−2,7)A(-2, 7) and B(2,−3)B(2, -3).

    Show the answer

    2y+5x−4=02y + 5x - 4 = 0

  2. (b)

    Given that 5b−a8b+3a=15\dfrac{5b - a}{8b + 3a} = \dfrac15, find, correct to two decimal places, the value of ab\dfrac ab.

Worked solution (try it first)

(a)

  1. Gradient =y2−y1x2−x1= \frac{y_2 - y_1}{x_2 - x_1}
    =−3−72−(−2)= \frac{-3 - 7}{2 - (-2)}
    =−104= \frac{-10}{4}
    =−52= -\frac52.
  2. Using the point A(−2,7)A(-2, 7): y−7=−52(x+2)y - 7 = -\frac52(x + 2).
  3. Multiply by 2: 2y−14=−5x−102y - 14 = -5x - 10.
  4. So 2y+5x−4=02y + 5x - 4 = 0.

(b)

  1. One fraction equals another, so cross-multiply: 5(5b−a)=1×(8b+3a)5(5b - a) = 1 \times (8b + 3a).
  2. Expand: 25b−5a=8b+3a25b - 5a = 8b + 3a.
  3. Collect the aa terms on one side and the bb terms on the other: 17b=8a17b = 8a.
  4. Divide both sides by 8b8b: ab=178=2.125\frac ab = \frac{17}{8} = 2.125.
  5. Correct to two decimal places: 2.132.13.

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