ace-test-series subject-test

Question

After taking |A|=0, I am getting x³+1=0 and not x³-1=0.
Is it x³+1=0 or x³-1=0?

Answer 1

|A| = x * ( x*x - 0 ) - (-1)(0 - (-1)(-1)) = 0 [expanding along the first row and |A| should be 0]

=> $x^3 - 1$ = 0

=> x = 1

Comments

Ya, i missed the '-' in multiplying 2nd parameter.

BTW, expansion of (x³-1) is (x-1)(x²+x+1), so x=1, and not -1, for real values of x. 

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Oh, sorry, that's a typo :P editing the answer.