Question 69

If $$xy = -18$$ and $$x^{2} + y^{2} = 85$$, then ﬁnd the value of (x + y).

Solution

Given : $$(x^2 + y^2) = 85$$ and $$xy = -18$$

Using $$(x + y)^2 = x^2 + y^2 + 2xy$$

=> $$(x + y)^2 = 85 + (2 \times -18)$$

=> $$(x + y)^2 = 85 - 36 = 49$$

=> $$(x + y) = \sqrt{49} = 7$$

=> Ans - (D)

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