Aspire Faculty ID #15278 · Topic: JAMIA MCA 2016 · Just now
JAMIA MCA 2016

If the roots of $x^3-9x^2+23x-15=0$ are in A.P., then their common difference is …

Solution

Let roots be $a-d,\;a,\;a+d$. Then sum $=3a=9 \Rightarrow a=3$. Sum of pairwise products $=3a^2-d^2=23 \Rightarrow 27-d^2=23 \Rightarrow d^2=4$. Hence $d=\pm2$.

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