Question

determine the best method to solve each system of equation.then solve the system.
1.x+2y=3; x+y=1
2.m+6n=-8; m=2n+8
3.a-b=6; a=2b+7
4.4x+y=15; -x-3x=-12
5.3c-d=14; c-d=2
6.x+2y=-9; y=4x

Answer 1

x+2y=3
x+ y=1
Subtract:
-> y = 2 => x = 1 -2 = -1
Thus ( -1, 1)

Answer 2

m+6n = -8
m -2n = 8
Subtract:
-> 8n = -16
=> n = -2,
=> m = 8 + 2 ( -2) = 4
Thus ( 4, -2)

Answer 3

a-b =6;
a-2b= 7
Subtract:
-> b = -1 => a = 6 -1 = 5
Thus (5, -1)

Answer 4

4x+y= 15;
x = -3y + 12
Substitute:
-> 4 (-3y + 12) +y = 15
-12y +48 + y = 15
=> y = ( 15 - 48)/ -11 = 3
then x = -3 * 3 + 12 = 3
Thus ( 3,3)

Answer 5

5. elimination method
6. substitution
You should get the concept by now. It's good practice to arrange these equations vertically.