\left \{ {{7x-y=10} \atop {12x+y=28}} \right.
…dodajemy stronami
19x=38
x=2
7*2-y=10
14-y=10
-y=-4
y=4
\left \{ {{x=2} \atop {y=4}} \right.
spr.
\left \{ {{7*2-4=10} \atop {12*2+4=28}} \right.
…
\left \{ {{5x-4y=12} \atop {2x+4y=18}} \right.
…dodajemy stronami
7x=30
x=\frac{30}{7}=4\frac{2}{7}
2x+4y=18
x+2y=9
4\frac{2}{7}+2y=9
2y=9-4\frac{2}{7}
2y=4\frac{5}{7}
y=4\frac{5}{7}*\frac{1}{2}=\frac{33}{7}*\frac{1}{2}=\frac{33}{14}=2\frac{5}{14}
\left \{ {{x=4\frac{2}{7}} \atop {y=2\frac{5}{14}}} \right.
spr.
5*4\frac{2}{7}-4*2\frac{5}{14}=5*\frac{30}{7}-4*\frac{33}{14}=\frac{150}{7}-\frac{132}{14}=\frac{150}{7}-\frac{66}{7}=12
dalej sprawdzenie zrób sam…
\left \{ {{13m-27n=76} \atop {7m+9n=54}} \right. drugie równanie mnożymy *3
\left \{ {{13m-27n=76} \atop {21m+27n=162}} \right.
…dodajemy stronami
34m=238
m=7
7m+9n=54
7*7+9n=54
49+9n=54
9n=54-49
9n=5
n=\frac{5}{9}
\left \{ {{m=7} \atop {n=\frac{5}{9}}} \right.
spr.
13*7-27*\frac{5}{9}=91-15=76
dalej sprawdzenie zrób sam…
cdn…