Question

18. If a²+b² = 6, a+b=4, then ab=?
(a) 10
(b) 5
(c)20
(d)7​

Answer 1

Since a+b=4 and a^2+b^2,

${a}^{2} + {b}^{2} = 6 \\ (a + b) ^{2} - 2ab = 6 \\ (4) ^{2} - 2ab = 6 \\ 16 - 2ab = 6 \\ 2ab = 16 - 6 \\ 2ab = 10 \\ ab = 5$

Therefore , ab=5

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