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Question

2) If the roots of the quadratic equation :
x2+Ax+ B=0 are tan 30° and tan 15° then the value of A-B=(a) 1(b) -1(c) 2(d) 3

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Solution

Dear Student,

The given quadratic equation is,x2+Ax + B = 0Now, tan 30 and tan 15 are the roots of the above equation.Now, tan 30 + tan 15 = -A ....1tan 30 . tan 15 = B .....2Adding 1 and 2, we gettan 30 + tan 15 + tan 30 . tan 15 = -A + B .....3Now, tan 45 = tan 30 + 151 = tan 30 + tan 151 - tan 30 . tan 15 1 - tan 30 . tan 15 = tan 30 + tan 15tan 30 + tan 15 + tan 30 . tan 15 = 1 Now, from 3, we get 1 = -A + BA - B = -1

Regards.

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