Find zeros of a polynomial and apply them

Ramiro Grant

Ramiro Grant

Answered question

2022-04-07

Find zeros of a polynomial and apply them to an another equation
If a and b are the zeros of quadratic polynomial x24x5, find the value of 1a3+1b3.

Answer & Explanation

anita1415snck

anita1415snck

Beginner2022-04-08Added 19 answers

Another way to approach it without solving the corresponding equation. One has
1a3+1b3=a3+b3a3b3=(a+b(a2ab+b2)a3b3=(a+b)[(a+b)23ab]a3b3
Since a+b=4 and ab=5, we conclude that
Hence, 1a3+1b3=4×(42+15)125=124125

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