Question

Use the elimination method to solve the following system of equations. x + 3y – z = 2 x – 2y + 3z = 7 x + 2y – 5z = –21

Answer 1

well here,
x + 3y – z=–21........................1
2 x – 2y + 3z=-21,,,,,,,,,,,,,,,,,,,,,,,2
7 x + 2y – 5z=-21 ..........................3
now
multiply eqn 1 by 2
2x+6y-2z=-42.........................4
subtrating 2-4
-8y+5z=21..............................5
multiply eqn 1 by 7
7x+21y-7z=-147........................7
subtrating 3 - 6
-19y+2z=126.............................8
z=(19y+126)/2.........................9
substituting value of z in 5
-8y+{5(19y+126)/2}=21...................................
now get value of y
substitute the value of y in eqn 5
get value of z
substitute value of y and z in 1
get value of x
............................gud luck