Question

Решите систему уравнения 3 способами:графического,методам подстановки, и обычный.
9x+4y=-2
x+y=-8

Answer 1

$1) left { {9x+4y=-2, } atop {x+y=-8;}} right. left { {y= frac{-9x-2}{4} , } atop {y=-x-8;}} right. left { {x=6, } atop {y=-14;}} right. \ (6;-14).$
$2) left { {9x+4y=-2, } atop {x+y=-8;}} right. left { {x=-y-8, } atop {9(-y-8)+4y=-2;}} right. \ -9y-72+4y=-2, \ -5y=70, \ y=-14, \ x=-(-14)-8, \ x=6, \ left { {x=6, } atop {y=-14;}} right. \ (6;-14).$
$3) left { {9x+4y=-2, } atop {x+y=-8;}} right. left { {9x+4y=-2, } atop {-4x-4y=32;}} right. \ 9x-4x=-2+32, \ 5x=30, \ x=6, \ 6+y=-8, \ y=-14, \ left { {x=6, } atop {y=-14;}} right. \ (6;-14).$