Question 42

If a - b = 3 and $$a^2 + b^2 = 25$$, then the value of ab is

Solution

Given : $$a^2 + b^2 = 25$$ ----------(i)

Also, $$a-b=3$$

Squaring both sides, we get :

=> $$(a-b)^2=(3)^2$$

=> $$a^2+b^2-2ab=9$$

=> $$25-2ab=9$$ [Using (i)]

=> $$2ab=25-9=16$$

=> $$ab=\frac{16}{2}=8$$

=> Ans - (B)

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