Simultaneous Equations

Generally speaking, if the coefficients of the second term are the same, that is the number you multiply by, and the signs are different, you add them, if the signs are the same you subtract them. If the coefficients are different then you have to multiply first by numbers that make the coefficients the same:

x+y=6
2x-y=6

add them because the y coefficients are the same and the signs different:

3x=12 so x=4 and y=2

x+y=6
2x+y=10

subtract them because the y coefficients are the same and the signs the same:

x=4 so y = 2

3x+4y=21
2x-3y= -3

multiply (1) by 3 and (2) by 4 then add them

9x+12y=63
8x-12y= -12

17x=51 so x=3 substituting in (1) 9+4y=21, 4y=12 so y=3

etc.

This page has been visited times