If the roots of the quadratic equation x 2 + p x + q = 0 are tan 3 0 ∘ and tan 1 5 ∘ , then the value of 2 + q − p is?
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You can use just tan(A+B)=tanA+tanB/1-tanAtanB tan(A+B)=tan(15+30)=1=(-p)/1-q so we get ans as 3 just by using sum of roots and product of roots concept.
The exact value of tan 1 5 = 2 − 3 from the formula: tan ( α − β ) = 1 + tan α tan β tan α − tan β , where 1 5 = 4 5 − 3 0
The exact value of tan 3 0 = 3 3
From Vieta's formulas, we know that:
tan 3 0 + tan 1 5 = − p
tan 3 0 × tan 1 5 = q
So long story short, solve for p and q
Quite an easy sum.So,I suppose no solution would be required for this one.
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Given equation
x 2 +px+q
Roots of the equation= tan 1 5 , tan 3 0
We know that
tan 1 5 =2- 3
tan 3 0 = 3 1
In the given equation
Sum of the roots = -p = 2- 3 + 3 1
⇒ p = 3 2 − 2 3
Product of the roots = q=(2- 3 )( 3 1 )
⇒ q= 3 2 − 3
Therefore 2+q-p = 2+ 3 2 − 3 - 3 2 − 2 3
⇒ 2+ 3 3
⇒ 2+1
⇒ 3