Class 10

Math

All topics

Quadratic Equations

Find the value of $x_{3}+9x_{2}−x+4$ for $x=−5+2−4 $

Consider the given expression.

$⇒x_{3}+9x_{2}−x+4$

Since, $x=−5+2−4 ⇒−5+4i$

Therefore,

$⇒(−5+4i)_{3}+9(−5+4i)_{2}−(−5+4i)+4$

$⇒(−125+64i_{3}−3×5×4i(−5+4i))+9(25+16i_{2}−2×5×4i)+5−4i+4$

$⇒(−125−64i−60i(−5+4i))+9(25−16−40i)+9−4i$

$⇒(−125−64i+300i−240i_{2})+9(9−40i)+9−4i$

$⇒115+236i+90−360i−4i$

$⇒205−128i$

Hence, this is the answer.