Question 43

If a - b = -7 and $$a^{2}$$ + $$b^{2}$$ = 85, then ﬁnd ab.

Given : $$(a - b) = -7$$ and $$a^2 + b^2 = 85$$

Using $$(a - b)^2 = a^2 + b^2 - 2ab$$

=> $$(-7)^2 = 85 - (2 \times ab)$$

=> $$2 ab = 85 - 49 = 36$$

=> $$ab = \frac{36}{2} = 18$$

=> Ans - (A)

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