A) 115
B) 110
C) 120
D) 125
Correct Answer: B
Solution :
[b] Since, \[~\alpha ,\beta \] be the roots of quadratic equation \[{{x}^{2}}-5x+1=0\] \[\therefore \alpha +\beta =5\And \alpha .\beta =1\] \[\therefore {{\alpha }^{3}}+{{\beta }^{3}}={{\left( \alpha +\beta \right)}^{3}}-3\alpha .\beta )\left( \alpha +\beta \right)\] \[={{\left( 5 \right)}^{3}}-3.1\times 5\] \[=125-15=110.\]
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