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If a - b = 5 and $a^2 + b^2 = 45$, then the value of ab is: |
25 10 15 20 |
10 |
(a – b)2 = a2 + b2 – 2ab = 52 = 45 - 2ab = 25 = 45 – 2ab = 2ab = 45 – 25 = 20 = ab = 10 |
