If you were to use the substitution method to solve the following system, choose the new equation after the expression equivalent to y from the second equation is substituted into the first equation.

2x - 7y = 4
3x + y = -17

Question

If you were to use the substitution method to solve the following system, choose the new equation after the expression equivalent to y from the second equation is substituted into the first equation.

2x - 7y = 4
3x + y = -17

mathslover · Answer

First of all, transpose 3x to the Right Hand Side. 
$$\large{3x+y=-17}$$
$$\large{y = -17-3x}$$

mathslover · Answer

Now put the above equation into the first one on the place of y

anonymous · Answer

All you do is rearrange the second equation to get y by itself. Then, you can plug it in where y is in the first equation. Just subtract 3x over to the other side to get y=-17-3x.

mathslover · Answer

@alexislovier what do you get now?

anonymous · Answer

uhm. i dont know

anonymous · Answer

Im horrible at math .

mathslover · Answer

As the first equation we have : 2x - 7y = 4

and from the above : y = -17-3x

Now put this value of y in the first equation : 2x - 7y = 4

$2x-7y=4$ 
But y = -17-3x

So : $2x- 7(-17-3x) =4$ 

Solve it now.

anonymous · Answer

so you substract 2x and 3x?

anonymous · Answer

hello?

mathslover · Answer

No! : first multiply 7 to the term : (-17-3x)

anonymous · Answer

From 2x-7(-17-3x)=4, you distribute the -7. So multiply both of the things in the parens by -7. That gives you 2x+119+21x=4. Then, simplify it to 23x+119=4. Subtract 119 from both sides to get 23x=-115. Divide both sides by 23. X is -5.

mathslover · Answer

we have : 

2x - 7(-17-3x) 

For solving this : we will do multiply (7) to (-17-3x) .. 

What do you get after multiplying @alexislovier

anonymous · Answer

Now, plug -5 back in for x in one of the original equations. Lets use (2x-7y=4). So (2(-5)-7y=4) Simplify and solve for y. That's -10-7y=4. Add -10 to both sides for -7y=14. Now divide both sides by -7 to get y=-2. Your answers are x=-5,y=-2.

anonymous · Answer

A. 2(3x - 17) - 7y = 4	
	 B. 2(-3x - 17) - 7y = 4	
	 C. 2x - 7(3x - 17) = 4	
	 D. 2x - 7(-3x - 17) = 4

anonymous · Answer

i have too get one of those

anonymous · Answer

Oh then you stop at this step. 2x-7(-17-3x)=4.

mathslover · Answer

That you have : $2x - 7(-17-3x) = 4$ which is the last option.

anonymous · Answer

ohhhhhh ok! got cha

mathslover · Answer

Good! also WELCOME TO OPENSTUDY

anonymous · Answer

can you guys help me with another one ?