If a and b are the roots of the equation x2 - 9x + 20 = 0, find the value of a2 + b2 + ab?  Choose the correct choice from the following options
A) 10	B) 25	C) 36	D) 61	E) 87
Explanation:   a2 + b2 + ab = a2 + b2 + 2ab - ab   i.e., (a + b)2 - ab   from x2 - 9x + 20 = 0, we have   a + b = 9 and ab = 20. Hence the value of required expression (9)2 - 20 = 61.   Answer 61
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If a and b are the roots of the equation x2 - 9x + 20 = 0, find the value of a2 + b2 + ab?