Question 60

If x+ 2y = a and x-2y=b, which of the following is and expression for xy ?

Solution

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Given,
x + 2y= a....(1)
x - 2y= b....(2)
(1) + (2): 2x=a + b
x=a+b/2
substituting x in (1) we get
y=a-b/4
∴ xy=$$(a^{2}-b^{2})$$/8

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