Question 69

If a - b = -5 and $$a^2 + b^2$$ = 73, then find ab.

Solution

Given : $$(a - b) = -5$$ and $$a^2 + b^2 = 73$$

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

=> $$(-5)^2 = 73 - (2 \times ab)$$

=> $$2 ab = 73 - 25 = 48$$

=> $$ab = \frac{48}{2} = 24$$

=> Ans - (D)

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