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Question
If a : b = c : d, prove that: (9a + 13b)(9c – 13d) = (9c + 13d)(9a – 13b).
Solution
Given, `a/b = c/d`
`=> (9a)/(13b) = (9c)/(13d)` ...`("Multiplying each side by" 9/13)`
`=> (9a + 13b)/(9a - 13b) = (9c + 13d)/(9c - 13d)` ...(By componendo and divdendo)
`=> (9a + 13b)(9c - 13d) = (9c + 13d)(9a - 13b)`
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