Question

2. Which of the following quadratic equation describe the speed of Raj's car?
a) x² - 5 X - 500 = 0
b) x² + 4x - 400 = 0
c) x² + 5x - 500 = 0
d) x² - 4x + 400 = 0
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Answer 1

Step-by-step explanation:

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Answer 2

Complete Question :- Refer to image .

Answer :-

→ speed of raj car = x km/h .

→ speed of ajay car = 5 km faster than speed of raj car = (x + 5) km/h .

so,

→ Distance cover by ajay in 2 hours = 2(x + 5) km. (Ans.i)

now,

→ time taken by raj to cover 400 km = D/S = (400/x) hours .

and,

→ time taken by ajay to cover 400km = D/S = 400/(x + 5) hours .

A/q,

→ 400/x - 400/(x + 5) = 4

→ 400{1/x - 1/(x + 5)} = 4

→ (x + 5 - x)/x(x + 5) = 1/100

→ x² + 5x = 5 * 100

→ x² + 5x - 500 = 0 (c) (Ans.ii)

solving this we get,

→ x² + 25x - 20x - 500 = 0

→ x(x + 25) - 20(x + 25) = 0

→ (x + 25)(x - 20) = 0

→ x = (-25) or 20 , since speed cant be in negative .

therefore, speed of raj's car is 20 km/h . (a) (Ans.iii)