[tex]a_1=4x-2\\a_2=5-x\\a_3=2x+5\\\\\left \{ {{a_3=a_1+2r} \atop {a_2=a_1+r}} \right. \\\left \{ {{2x+5=4x-2+2r} \atop {5-x=4x-2+r}} \right. \\\left \{ {{5+2=4x-2x+2r} \atop {5+2=4x+x+r}} \right. \\\left \{ {{7=2x+2r/*(-5)} \atop {7=5x+r /*2}} \right. \\\\\left \{ {{-35=-10x-10r} \atop {14=10x+2r}} \right. \\-21=-8r /:(-8)\\\frac{-21}{-8}=r\\r=2\frac58\\7=5x+r\\7=5x+2\frac58 /-2\frac58\\7-2\frac58=5x\\4\frac38=5x /*\frac15\\\frac{35}8*\frac15=x\\\frac78=x[/tex]
[tex]a_1=4*\frac78-2=\frac72-2=\frac32\\a_2=5-\frac78=4\frac18\\a_3=2*\frac78+5=\frac{14}8+5=5\frac{14}8=6\frac68=6\frac34[/tex]
