$=(x-1)(x-3)(x-5)(x-7)$$-65$
$=(x-1)(x-7)(x-3)(x-5)$$-65$
$=\left\lbrace x(x-7)-1(x-7)\right\rbrace$$\left\lbrace x(x-5)-3(x-5)\right\rbrace-65$
$=\left(x^2-7x-x+7\right)$$\left(x^2-5x-3x+15\right)-65$
$=\left(x^2-8x+7\right)$$\left(x^2-8x+15\right)-65$
$=\left(x^2-8x+7\right)$$\left(\underline{x^2-8x+7}+8\right)-65$
ধরি,
$x^2-8x+7=p$
তাহলে প্রদত্ত রাশি দাঁড়ায়,
$p\left(p+8\right)-65$
$=p^2+8p-65$
$=p^2+13p-5a-65$
$=p\left(p+13\right)-5\left(a+13\right)$
$=\left(p+13\right)\left(p-5\right)$
$=\left(x^2-8x+7+13\right)$$\left(x^2-8x+7-5\right)$
[ মান বসিয়ে ]
$=\left(x^2-8x+20\right)$$\left(x^2-8x+2\right)$ [Answer]