Ребят помогите!!! кто решит тому сотку скину на киви!!!

№1
a) $left { {{2x-3y=-8} atop {x^2-2xy-y^2=1}} right.$
Если $(-1;2)$ , то
$left { {{2*(-1)-3*2=-8} atop {(-1)^2-2*(-1)*2}-2^2=1} right. left { {{-2-6=-8} atop {1+4-4=1}} right. left { {{-8=-8} atop {1=1}} right.$
б) $left { {{x-y=-3} atop {1-xy=-2}} right.$
Если $(-1;2)$ , то
$left { {{-1-2=-3} atop {1-(-1)*2=-2}} right. left { {{-3=-3} atop {3=-2}} right.$
Ответ: не является
№2
$left { {{x+5y=7} atop {2x+3y=7}} right. left { {{x=7-5y} atop {2(7-5y)+3y=7}} right. left { {{x=7-5y} atop {14-10y+3y=7}} right. left { {{x=7-5y} atop {-7y=-7}} right. left { {{x=7-5} atop {y=1}} right. left { {{x=2} atop {y=1}} right.$
Ответ: $(2;1)$
№3
$left { {{3x-y=7 atop {5x+2y=8}} right. left { {{6x-2y=14} atop {5x+2y=8}} right. |+ left { {{3x-y=7} atop {11x=22}} right. left { {{6-y=7} atop {x=2}} right. left { {{y=-1} atop {x=2}} right.$
Ответ: $(2;-1)$
№4
$left { {{2x+3y=12} atop {x-y=1}} right. left { {{3y=12-2x} atop {y=x-1}} right. left { {{y=4- frac{2}{3}x } atop {y=x-1}} right.$
№5
$6x-5y$
$left { {{x+3y=6} atop {2x-y=5}} right. left { {{-2x-6y=-12} atop {2x-y=5}} right. left { {{x+3y=6} atop {-7y=-7}} right. left { {{x+3=6} atop {y=1}} right. left { {{x=3} atop {y=1}} right.$
$6*3-5*1=18-5=13$
№6
$left { {{ax+3y=9b} atop {5x+ay=b}} right.$
$(1;-1)$
$left { {{a-3=9b} atop {5+a=b}} right. left { {{a-9b=3} atop {a-b=-5}} right. left { {{a-9b=3} atop {-a+b=5}} right.|+ left { {{-8b=8} atop {a-b=-5}} right. left { {{b=-1} atop {a+1=-5}} right. left { {{b=-1} atop {a=-6}} right.$