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The area of a right triangle ABC is 7 and the perimeter is 14. What is the longer leg of the triangle?

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Answer:

The longer leg measures 4 + √2.

Explanation:

Let a = length of the short leg.

Let b = length of the long leg.

Let c = length of the hypotenuse.

area = ab/2

perimeter = a + b + c

Pythagorean theorem: a² + b² = c²

ab/2 = 7

a + b + c = 14

a² + b² = c²

ab = 14

a + b + c = 14

a² + b² = c²

b = 14/a

c = 14 - a - b

a² + b² = c²

b = 14/a

c = 14 - a - b

a² + 196/a² = (14 - a - b)²

a² + 196/a² = (14 - a - 14/a)²

a² + 196/a² = 196 - 14a - 196/a - 14a + a² + 14 - 196/a + 14 + 196/a²

0 = 196 - 14a - 196/a - 14a + 14 - 196/a + 14

0 = 196a - 14a² - 196 - 14a² + 14a - 196 + 14a

28a² - 224a + 392 = 0

a² - 8a + 14 = 0

a² - 8a + 16 = -14 + 16

(a - 4)² = 2

a - 4 = ±√2

a = 4 ± √2

Let a = 4 - √2 (short leg)

ab/2 = 7

(4 - √2)b/2 = 7

(4 - √2)b = 14

b = 14/(4 - √2)

b = 14/(4 - √2) × (4 + √2/(4 + √2)

b = 14(4 + √2)/(16 - 2)

b = 14(4 + √2)/14

b = 4 + √2 (long leg)

a + b + c = 14

4 + √2 + 4 - √2 + c = 14

8 + c = 14

c = 6 (hypotenuse)

Answer: The longer leg measures 4 + √2.

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