Question

помогите решить первые 3 вопроса

Answer 1

$1)\ \ \dfrac{6}{a^2-3a}-\dfrac{2}{a}=\dfrac{6}{a(a-3)}-\dfrac{2}{a}=\dfrac{6-2(a-3)}{a(a-3)}=\dfrac{12-2a}{a(a-3)}=\dfrac{2(6-a)}{a(a-3)}\\\\\\\dfrac{a+c}{ac}\cdot \dfrac{5ac^2}{c^2-a^2}=\dfrac{a+c}{1}\cdot \dfrac{5c}{(c-a)(c+a)}=\dfrac{5c}{c-a}$

$2)\ \ 3+\dfrac{x-1}{3}=\dfrac{x-2}{5}\ \Big|\cdot 15\\\\\\45+5(x-1)=3(x-2)\\\\45+5x-5=3x-6\\\\2x=-46\ \ ,\ \ \ x=-23$

$3)\ \ Q=cm(t_2-t_1)\ \ \ \to \ \ \ \ t_2-t_1=\dfrac{Q}{cm}\ \ \ ,\ \ \ t_1=t_2-\dfrac{Q}{cm}\ \ ,\\\\t_1=\dfrac{c\, m\, t_2-Q}{c\, m}$