How to solve simultaneously for x and y?

Question

help please im doing hon pre calc review and need help please show work

c) 7x +2y = ¡4

3x +4y = 14

e) x+ 2y = 5

2x+ 4y = 1

Answer 1

The trick here is to get one of the 2 expressions to the form:

x = ay + b

and to fill in that value for x in the other expression.

I won't do c) 'cause I don't know what the i stands for.

e)

x + 2y = 5

x = 5 - 2y

2x + 4y = 1

2x = 1-4y

x = 0.5 - 2y

(x = 5 - 2y, fill that in)

5 - 2y = 0.5 - 2y

hmm, now thats wierd. Maybe it's me but are you sure you copied that  correctly from your book?

Cause this equations imply that  5 = 0.5

peculiar huh :-P

Answer 2

heehee your a hippie

Answer 3

You can figure out the answers for these by using substitution. Let's start with the first one:

(try to get either the x or the y on its own)

7x + -7x +2y = -4 + -7x

2y = -4 + -7x

(2y)/2 = (-4 + -7x)/2

y = (-2 + -7/2x)

(now subsitute in the other equation (-2 + -7/2x) for y)

3x + 4(-2 + -7/2x) =14

3x + -8 + -14x =14

-11x = 22

x = -2

(now you know x=-2. plug -2 into one of the two equations to find y)

7(-2)+2y = -4

2y = 10

y = 5

Your answer for the first one is x = -2 and y = 5.

Now, try the other problem using the same method.

Answer 4

how can you have two differnt variables?

Answer 5

c the answer says j4?

On e, if you multiply everything in the first row by 2, you get 2x + 4y = 10

There is no way 2x + 4y can equal 10 and 1 at the same time so there is no solution for question e.