Question
If 5x + 9y = 5 and 125x3 + 729y3 = 120, then the value of the product of x and y is?
Answer: Option C
5x + 9y = 5 . . . . . (i)
125x3 + 729y3 = 120 . . . . . (ii)
From equation (i) cubing both sides
⇒ (5x + 9y)3 = 53
⇒ 125x3 + 729y3 + 3 × 5x × 9y(5x + 9y) = 125
⇒ 125x3 + 729y3 + 135xy × 5 = 125
⇒ 120 + 135xy × 5 = 125
⇒ 135xy × 5 = 5
⇒ xy = $$\frac{1}{{135}}$$
∴ product of x & y = $$\frac{1}{{135}}$$
Was this answer helpful ?
5x + 9y = 5 . . . . . (i)
125x3 + 729y3 = 120 . . . . . (ii)
From equation (i) cubing both sides
⇒ (5x + 9y)3 = 53
⇒ 125x3 + 729y3 + 3 × 5x × 9y(5x + 9y) = 125
⇒ 125x3 + 729y3 + 135xy × 5 = 125
⇒ 120 + 135xy × 5 = 125
⇒ 135xy × 5 = 5
⇒ xy = $$\frac{1}{{135}}$$
∴ product of x & y = $$\frac{1}{{135}}$$
Was this answer helpful ?
More Questions on This Topic :
Question 2. If **Hidden Equation** = ?....
Question 3. If **Hidden Equation** is?
Question 6. If **Hidden Equation** is?
Question 9. **Hidden Equation** 3 = ?
Latest Videos
Latest Test Papers
Submit Solution