Question

I don't know how to solve this by elimination 4c - 3d=1 2c + 4d=17

Answer 1

4 c - 3 d = 1 , 2 c + 4 d = 17

Multiply the second equation by 2.

4 c + 8 d = 34

Now:

4 c - 3 d = 1
-
4 c + 8 d = 34
_____________

4 c - 4 c - 3 d - 8 d = 1 - 34

- 11 d = - 33

Divide both sides by -11.

- 11 d / - 11 = - 33 / - 11

d = 3

Now let's plug d = 3 in an original equation:

4 c − 3 d = 1

4 c − 3 ∙ 3 = 1

4 c − 9 = 1

Add 9 to both sides.

4 c = 10

Divide both sides by 4

c = 10 / 4 = 2 ∙ 5 / 2 ∙ 2

c = 5 / 2

Answer:

c = 5 / 2 and d = 3