Question

Найдите значение выражения (x^2+2x-15)/(x+5)-(x+6) при x = 18.

Answer 1

$\frac{(18^{2} + 2 \times 18 - 15) }{(18 + 5) - (18 + 6)} = \frac{18^{2} + 36 - 15 }{ 23 - 24} = \frac{18^{2} + 21 }{ - 1} = \frac{345}{ - 1} = - 345$

Answer 2

$a)\ \ x=18\\\\\dfrac{x^2+2x-15}{x+5}-(x+6)=\dfrac{(x+5)(x-3)}{x+5}-(x+6)=x-3-x-6=-9\\\\\\\\b)\ \ \dfrac{x^2+2x-15}{(x+5)-(x+6)}=\dfrac{(x+5)(x-3)}{-1}=-(18+5)(18-3)=-23\cdot 15=-345$