Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**Gabrielle****Guest**

8.

y = (1/2)x - 3

y = (3/2)x 1

y = (1/2)x 3

(3/2)x 1 = (1/2)x 3

+1 +1

(3/2)x = (1/2)x 4

(4/2)x = -4

2x = -4

x = -2

y = (3/2)x 1

y = (3/2)-2 1

y = -3 1

y = -4

(-2, -4)

12.

4x + 3y = -15

y = x + 2

y = x + 2 (times equation by 3)

3y = 3x + 6

4x + 3y = -15

7x = -21

x = -3

y = x + 2

y = -3 + 2

y = -1

(-3, -1)

16.

y = -2x + 1

y = x 5

0 = 3x + 6

3x = 6

x = 2

y = x 5

y = 2 5

y = -3

(2, -3)

Im not sure what I did wrong for these.. my teacher keeps telling me this

#8 - Tell me what you did to get from the first step to the second.

(3/2)x=(1/2)x-2

(4/2)x= -2

#12 - The work must show elimination. You have used substitution. Try again.

#16 - I don't see your elimination work. Please look at the example that I provided in my last post to help you show your work for #12 and #16.

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,207

hi Gabrielle,

8.

y = (1/2)x - 3

y = (3/2)x what sign is missing here? 1

y = (1/2)x 3

(3/2)x 1 = (1/2)x 3

+1 +1

(3/2)x = (1/2)x 4

(4/2)x = -4

2x = -4

x = -2

y = (3/2)x 1

y = (3/2)-2 1

y = -3 1

y = -4

(-2, -4)

12.

4x + 3y = -15

y = x + 2

y = x + 2 (times equation by 3)

3y = 3x + 6 ........................A

4x + 3y = -15 ..........................B

7x = -21

x = -3

y = x + 2

y = -3 + 2

y = -1

(-3, -1)

This answer is correct and it looks like you have used elimination. You can make this clear by lettering the equations and then stating what you are doing to eliminate y.

eg A - B gives 3y - 4x - 3y = 3x + 6 - (-15)

-4x = 3x +21

etc

16.

y = -2x + 1

y = x wthat sign is missing here? 5

0 = 3x + 6

3x = 6

x = 2

y = x 5

y = 2 5

y = -3

(2, -3)

Im not sure what I did wrong for these.. my teacher keeps telling me this

#8 - Tell me what you did to get from the first step to the second.

(3/2)x=(1/2)x-2

(4/2)x= -2

This step is wrong. If you subtract (1/2)x from each side you should have x = -2

#12 - The work must show elimination. You have used substitution. Try again.

#16 - I don't see your elimination work. Please look at the example that I provided in my last post to help you show your work for #12 and #16

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline