Question

Фото алгебра срочно;

Answer 1

$8)\; \; \left\{\begin{array}{l}2\, (3x-y)-5=2x-3y\\5-(x-2y)=4\, (y+4)\end{array}\right\; \; \left\{\begin{array}{l}6x-2y=2x-3y\\5-x+2y=4y+16\end{array}\right\; \; \left\{\begin{array}{l}4x=-y+5\\-x=2y+11\end{array}\right\\\\\\\left\{\begin{array}{l}y=-4x+5\\-x=-8x+21\end{array}\right\; \; \left\{\begin{array}{l}y=-4x+5\\7x=21\end{array}\right\; \; \left\{\begin{array}{l}y=-7\\x=3\end{array}\right$

$9)\; \; \dfrac{2x+1}{3}-\dfrac{7x+5}{15}=\dfrac{x-2}{5}+\dfrac{2}{3}\; \Big|\cdot 15\\\\\\5(2x+1)-(7x+5)=3(x-2)+10\\\\10x+5-7x-5=3x-6+10\\\\3x=3x+4\; \; \to \; \; 3x-3x=4\; \; \; \to\; \; \; \underline {0=4\; neverno}\\\\Otvet:\; \; x\in \varnothing \; .$

$10)\; \; \left\{\begin{array}{l}(a-3)x-by=3b\\ax-(2b-1)y=3a-11\end{array}\right\\\\\\(-1;2)\; \; \to \; \; x=-1\; ,\; y=2:\; \; \left\{\begin{array}{l}-(a-3)-2b=3b\\-a-2(2b-1)=3a-11\end{array}\right\\\\\\\left\{\begin{array}{l}a+5b=3\, |\cdot (-4)\\4a+4b=13\end{array}\right\; \; \left\{\begin{array}{l}a+5b=3\\-16b=1\end{array}\right\; \; \left\{\begin{array}{l}a=\frac{53}{16}\\b=-\frac{1}{16}\end{array}\right$