Question

Решить систему уравнений :
а)
4х+15у=-42
-6х+25у=-32

 в)
12х-35у=25
-8х-15у=-55

 

Answer 1

а)
$left { {{4x+15y=-42} atop {-6x+25y=-32}} right. Rightarrow left { {{12x+45y=-126} atop {-12x+50y=-64}} right. Rightarrow left { {{95y=-190} atop {-12x+50y=-64}} right. Rightarrow$
$Rightarrowleft { {{y=-2} atop {12x=-36}} right. Rightarrow left { {{y=-2} atop {x=-3}} right.$
 в)  
$left { {{12x-35y=25} atop {-8x-15y=-55}} right. Rightarrow left { {{24x-70y=50} atop {-24x-45y=-165}} right. Rightarrow left { {{-115y=-115} atop {-8x-15y=-55}} right. Rightarrow$
$Rightarrow left { {{y=1} atop {8x=40}} right. Rightarrowleft { {{y=1} atop {x=5}} right.$