QQuestion
A(−10, −2) and B(2, 10) are two end points of a line segment. If AB intersects the x-axis at P, find the:
(a) ratio in which P divides AB.
(b) coordinates of point P.
A(−10, −2) and B(2, 10) are two end points of a line segment. If AB intersects the x-axis at P, find the:
(a) ratio in which P divides AB.
(b) coordinates of point P.
(a) Let P(x, 0) divide AB internally in the ratio m : n.
Using the section formula for the y-coordinate,
y = \frac{\mathrm{m}\mathrm{y}_2+\mathrm{n}\mathrm{y}_1}{\mathrm{m}+\mathrm{n}}
Since P lies on the x-axis, y = 0.
0 = \frac{\mathrm{m}(10)+\mathrm{n}(-2)}{\mathrm{m}+\mathrm{n}}
⇒ 10m − 2n = 0
⇒ 10m = 2n
⇒ \frac{\mathrm{m}}{\mathrm{n}}=\frac{2}{10}=\frac{1}{5}
Therefore, P divides AB in the ratio 1 : 5.
(b) Using the section formula for the x-coordinate,
x = \frac{\mathrm{m}\mathrm{x}_2+\mathrm{n}\mathrm{x}_1}{\mathrm{m}+\mathrm{n}}
Here, m = 1, n = 5, x₁ = −10 and x₂ = 2.
x = \frac{1(2)+5(-10)}{1+5}
x = \frac{2-50}{6}
x = \frac{-48}{6} = −8
Since P lies on the x-axis, y = 0.
Therefore, P = (−8, 0).
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