I am trying to scrub up on some maths for a uni course and am using cliff quick review books.
I am in the section solving equations (with two variables) using addition/subtraction method.
One questions asks : Solve for x and y
8x+2y=7
3x-4y=5
ans x=1 y=-1/2
I understand this is the answer but I cannot get there using the method.. Can someone please show me the workings Please pretty please :)
+33653 Before you add or subtract two equations in two unknowns you want to adjust them so that one unknown is multiplied by the same magnitude number in both equations. This way, when you add or subtract them that unknown disappears and you are left with just one.
Using your equations
8x + 2y = 7 ...(1)
3x - 4y = 5 ...(2)
If only the first equation had 4y instead of 2y we could get rid of the y terms by adding the two equations.
We can make it have 4y instead of 2y by multiplying every term in the equation by 2.
16x + 4y = 14 ...(3)
Now let's add equations (2) and (3) term by term:
3x + 16x - 4y + 4y = 5 + 14
19x = 19
Divide both sides by 19
x = 1
Now replace x in one of your original equations by 1:
8*1 + 2y = 7
2y = -1
Divide both sides by 2
y = -1/2
+33653 Before you add or subtract two equations in two unknowns you want to adjust them so that one unknown is multiplied by the same magnitude number in both equations. This way, when you add or subtract them that unknown disappears and you are left with just one.
Using your equations
8x + 2y = 7 ...(1)
3x - 4y = 5 ...(2)
If only the first equation had 4y instead of 2y we could get rid of the y terms by adding the two equations.
We can make it have 4y instead of 2y by multiplying every term in the equation by 2.
16x + 4y = 14 ...(3)
Now let's add equations (2) and (3) term by term:
3x + 16x - 4y + 4y = 5 + 14
19x = 19
Divide both sides by 19
x = 1
Now replace x in one of your original equations by 1:
8*1 + 2y = 7
2y = -1
Divide both sides by 2
y = -1/2
