My First Quadratic

Algebra Level 3

The value of a a for which the sum of the squares of the roots of the equation x 2 ( a 2 ) x a 1 = 0 x^2 - (a-2)x - a - 1 = 0 assumes the least value is?


The answer is 1.

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1 solution

Aareyan Manzoor
Feb 19, 2015

let the roots be α , β \alpha,\beta , by vieta's, α 2 + β 2 = ( a 2 ) 2 2 ( a 1 ) \alpha^2+\beta^2 =(a-2)^2-2(-a-1) a 2 2 a + 6 = ( a 1 ) 2 + 5 a^2-2a+6=(a-1)^2+5 it will obtain its minima at 1 for ( a 1 ) 2 = 0 (a-1)^2=0 . hence the answer is 1.

Yeah, exactly what I did ! The question is overrated though....

Venkata Karthik Bandaru - 6 years, 3 months ago

Can't understand @Aareyan Manzoor

Abdur Rehman Zahid - 6 years, 2 months ago

It should be ( a 2 ) 2 2 ( a 1 ) (a-2)^2 - 2(-a-1)

Ariel Gershon - 6 years, 2 months ago

I used the same approach :)

Curtis Clement - 6 years, 2 months ago

it should be (a-2)^2 in the 1St line

Vishal Mahto - 6 years, 2 months ago

(a-2)^2 +2(a+1)

Vishal Mahto - 6 years, 2 months ago

alpha + beta = a-2 and not a+1 pls note that

Anand O R - 6 years ago

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