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If a3 + b3 = 218 and a + b = 2, then the value of $$1 - \sqrt {ab} $$ is:
Answer & Solution
Correct Answer:
Option
D
$$\eqalign{
& {a^3} + {b^3} = 218\,\& \,a + b = 2 \cr
& {\left( {a + b} \right)^3} = {\left( 2 \right)^3} \cr
& {a^3} + {b^3} + 3\left( {a + b} \right)\left( {ab} \right) = 8 \cr
& 218 + 3\left( 2 \right)\left( {ab} \right) = 8 \cr
& ab = \frac{{8 - 218}}{6} \cr
& ab = \frac{{ - 210}}{6} = - 35 \cr
& \sqrt {1 - ab} = \sqrt {1 - \left( { - 35} \right)} \cr
& \sqrt {1 - ab} = \sqrt {1 + \left( {35} \right)} \cr
& \sqrt {1 - ab} = 6 \cr} $$
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