Question

.....способом подстановки​

Answer 1

Ответ:

а) (x, y)=(9, 2)

b) (x, y)=(1, 1)

c) (x, y)=(-8, -5/8)

d) (x, y)=(-2/5, -3/5)

Пошаговое объяснение:

a)

$\left \{ {{x-y=7} \atop {x+y=11}} \right. =\left \{ {{x-y=7} \atop {x=11-y}} \right. = 11-y-y=7=2\\\\x=11-2\\x=9\\\left \{ {{9-2=7} \atop {9+2=11}} \right.= (x, y)=(9, 2)$

b)

$\left \{ {{2x+y=3} \atop {3x+5y=8}} \right. = \left \{ {{y=3-2x} \atop {3x+5y=8}} \right. = 3x+5(3-2x)=8\\x=1\\y= 3-2*1\\y= 1\\\left \{ {{2*1+1=3} \atop {3*1+5*1=8}} \right. = \left \{ {{3=3} \atop {8=8}} \right.\\(x, y)=(1, 1)$

c)

$\left \{ {{x=-8} \atop {4x-8y=-27}} \right. = 4x*(-8)-8y=-27\\x=-8\\y= -\frac{5}{8}\\\left \{ {{-8=-8} \atop {-27=-27}} \right.\\(x, y)=(-8, -\frac{5}{8} )$

d)

$\left \{ {{7x+7y=-7} \atop {10x+2y=-5,2}} \right. = \left \{ {{7x+7y=-7} \atop {x=-0,52-\frac{1}{5}y }} \right. = 7(-0,52-\frac{1}{5}y )+ 7y=-7\\y = -\frac{3}{5} \\x = -0,52-\frac{1}{5}*(-\frac{3}{5} )\\x = -\frac{2}{5}\\y = -\frac{3}{5}\\(x, y)=(-\frac{2}{5}, -\frac{3}{5} )\\\left \{ {{7*(-\frac{2}{5})+7*(-\frac{3}{5} )= -7} \atop {10*(-\frac{2}{5})+2*(-\frac{3}{5} )= -5,2}} \right.$