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Question
The side (in cm) of a triangle containing the right angle are 5x and 3x – 1. If the area of the triangle is 60 cm². Find the sides of the triangle.
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Solution
Area of the right triangle ABC
= `(5x (3x - 1))/(2)`
∴ `(5x (3x - 1))/(2)` = 60
⇒ 15x2 - 5x = 120
⇒ 3x2 - x = 24
⇒ 3x2 - x - 24 = 0
⇒ 3x2 - 9x + 8x - 24 = 0
⇒ 3x(x - 3) + 8(x - 3) = 0
⇒ (x - 3) (3x + 8) = 0
⇒ x - 3 = 0 or 3x + 8 = 0
⇒ x = 3 or x = `(-8)/(3)`
But x = `(-8)/(3)` is not possible as isde cannot be - ve.
Then x = 3.
Hence, sides are AB = 3x - 1 = 8 cm
BC = 5x = 15 cm
Also from AC
= `sqrt(("AB")^2 + ("BC")^2)`
= `sqrt(64 + 225)`
= `sqrt(289)`
= 17 cm.
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