7.Binomial Theorem
normal

 $x^3 - 3x^2 - 9x + c$ ને $(x - a)^2 (x - b)$ પણ લખી શકાય તો $c$ ની કિમત મેળવો 

A

$-5$ અથવા $27$

B

$5$ અથવા $-27$

C

$5$ અથવા $27$

D

$-5$ અથવા $-27$

Solution

$2 a+b=3, a^{2}+2 a b=-9$

$\Rightarrow a^{2}+2 a(3-2 a)=-9$

$\Rightarrow a^{2}-4 a^{2}+6 a+9=0$

$\Rightarrow-3 a^{2}+6 a+9=0$

$\Rightarrow a^{2}-2 a-3=0$

$\Rightarrow(a+1)(a-3)=0$

$a=-1,3$

$c=-a^{2} b$

$\therefore a=-1, b=5;$

$a=3, b=-3$

$\therefore c=-5$ or $27$

Standard 11
Mathematics

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