Question

решите систему уравнений :
а) 2х+у=5
3х-4у=5
б) х-2у=-1
3х+4у=17
в) 2х-6у=0
х+у=-4
г)3,2х-1,2у=2
0,5х+0,6у=1,1

Answer 1

a)
$\left \{ {{2x + y=5} \atop {3x - 4y =5}} \right.$⇒ $\left \{ {{8x +4y=20} \atop {3x-4y=5}} \right.$ ⇒ 5x=15⇒x=3 
$\left \{ {{x=3} \atop {2*3 + y=5}} \right.$ ⇒ $\left \{ {{x=3} \atop {y=-1}} \right.$
b) 
$\left \{ {{x-2y=-1} \atop {3z+4y=17} \right.$⇒$\left \{ {{2x-4y=-2} \atop {3x+4y=17}} \right.$⇒$\left \{ {{x=19} \atop {19-2y=-1}} \right.$⇒$\left \{ {{x=19} \atop {y=10}} \right.$