[tex]a)\\ \left \{ {{2x-2y=7\ /*(-2)} \atop {{4x+3y=21 }} \right.\\ \left \{ {{-4x+4y=-14} \atop {{4x+3y=21 }} \right.\\ -------\\ 7y=7\ /:7\\ y=1\\ \\ 2x-2y=7\\ 2x-2*1=7\\ 2x=9\ /:2\\ x=4,5\\ \\ \left \{ {{x=4,5} \atop {y=1}} \right. [/tex]
[tex]b)\\ \left \{ {{2x+3y=14\ /*2} \atop {3x-2y=8\ /3}} \right. \\ \left \{ {{4x+6y=28} \atop {9x-6y=24}} \right. \\ -------\\ 13x=52\ /:13\\ x=4\\ \\ 2x+3y=14\\ 2*4+3y=14\\ 3y=6\ /:3\\ y=2\\ \\ \left \{ {{x=4} \atop {y=2}} \right.[/tex]
[tex]c)\\ \left \{ {{\frac{1}{2}x-2y=8\ /*(-4)} \atop {2x+5y=6}} \right.\\ \left \{ {{-2x+8y=-32} \atop {2x+5y=6}} \right.\\ -------\\ 13y=-26\ /:13\\ y=-2\\ \\ \frac{1}{2}x-2y=8\\ \frac{1}{2}x-2*(-2)=8\\ \frac{1}{2}x=4\ /*2\\ x=8[/tex]
[tex]d)\\ \left \{ {{\frac{1}{2}x-\frac{3}{4}y=0\ /*5} \atop {\frac{2}{3}x+1\frac{1}{4}y=9\ /*3 }} \right. \\ \left \{ {{\frac{1}{2}x-\frac{15}{4}y=0} \atop {\frac{2}{3}x+\frac{15}{4}y=9 }} \right. \\ -------\\ \frac{27}{6}x=27\ /*\frac{6}{27}\\ x=6\\ \\ \frac{1}{2}x-\frac{3}{4}y=0 \\ \frac{1}{2}*6-\frac{3}{4}y=0 \\ -\frac{3}{4}y=3\ /*(-\frac{4}{3})\\ y=-4\\ \\ \left \{ {{x=6} \atop {y=-4}} \right.[/tex]
Liczę na najlepsze :)
