Question

PLEASE HELP ME. Explain, in complete sentences, how you would use the elimination method to solve the following system of equations. Provide the solution to the system.

5x – 3y = 1
7x – 4y = 2

Answer 1

http://www.wolframalpha.com/input/?i=5x+%E2%80%93+3y+%3D+1+7%2C+x+%E2%80%93+4y+%3D+2&asynchronous=false&equal=Submit

Answer 2

Let's number our equations:
5x – 3y = 1 (1)
7x – 4y = 2 (2)
First the y seems easiest to eliminate; multiply (1) by 4 and (2) by -3 to get
20x – 12y = 4 (1)
-21x + 12y = -6 (2)
Now add (1) and (2) and the y's will cancel:
-x=-2 --------> x=2
now that we know the value of x we can use either equation to solve for y, let's use (1)
y=(1/3)(5x-1)=(5(2)-1)/3=3
so x=2 y=3
check your work by plugging these values into the original system and see if they yield true statements.

Answer 3

thnks for your help...I have one question..you multiply equation (1) by 4 and equation (2) by -3..shouldnt it be -4 for (1) ??

Answer 4

Not if you're going to ADD (1) to (2) to eliminate the y's. If you multiply (1) by -4 then you have to SUBTRACT it from (2) to eliminate the y's. I like to only add equations when possible, it helps me keep track of all the minus signs. When you subtract a whole equation it is like adding its negative, so when multiplying (1) by -4 and then subtracting (2) it seems to over-complicate the situation and it is more likely you will lose track of a minus sign somewhere.

I looked for another question on your page but I just saw this one posted twice.

Answer 5

thank you sooo much for your help