Question

Substitution method

1) 3x + y = 7
4x + 2y = 16

2) 2x + 2y = 4
X - 2y = 0

Answer 1

`1.)\\ \\\begin{cases}3x + y = 7 /*(-2)\\ 4x + 2y = 16 \end{cases} \\ \\\begin{cases}-6x-2y =-14 \\ 4x + 2y = 16 \end{cases}\\-------\\-2x=2/:(-2)\\ \\x=-2`


`3*(-1) + y = 7\\ \\-3+y=7\\ \\y=7+3\\ \\y=10\\ \\\begin{cases}x=-1\\ y=10 \end{cases}`




`2.)\\ \\\begin{cases}2x + 2y = 4 \\x - 2y = 0 \end{cases} \\-------- \\ 3x=4/:3\\ \\x=(4)/(3)\\ \\2*(4)/(3)+ 2y = 4 \\ \\`


`2y=(12)/(3)-(8)/(3)\\ \\2y=(4)/(3)/*((1)/(2))\\ \\y=(2)/(3)\\ \\\begin{cases}x=(4)/(3) \\y=(2)/(3)\end{cases}`

Answer 2

1. y=7-3x
4x+2(7-3x)=16
4x+14-6x=16
-2x=2
x=-1
-3+y=7
y=10
(-1,10)

2. x=2y
2(2y)+2y=4
4y+2y=4
6y=4
y=2/3
x-2(2/3)=0
x-4/3=0
x=4/3
(4/3,2/3)