Simultaneous equations ( questions mostly )

Question 1

If the signs are the SAME to you subtract or add them?

Answer 1

Subtract

Question 2

Do you add or subtract if the signs are DIFFERENT?

Answer 2

Add

Question 3

5x + 2y = 20

2x + 4y = 24

Answer 3

10x + 4y = 40
- 2x +4y = 24

11x = 66
x=6 y=4

Question 4

y = 2x + 3

2x + 3y = 23

Answer 4

2x + 3(2x - 3) = 23
2x + 6x - 9 = 23
8x - 9 = 23
8x = 32
x = 4

Question 5

y = x* + 1
y = x + 3

Answer 5

x + 3 = x* + 1
x* + 1 - x - 3 = 0
x* - x - 2 = 0
(x + 1) ( x-2)=0

x= -1 / x= 2
y= 2 / y=5

Question 6

x* + y* = 25

y = 2x -2

Answer 6

x* + (2x - 2)* = 25
(2x -2) (2x-2)
4x* - 8x + 4
5x* - 8x + 4 = 25