Question

if x+y=2 and 2x-y=1 then what is the value of m if mx +y =0​

Answer 1

$\sf\huge {\underline{\underline{{Solution}}}}$

x+y= 2-------(1)

2x-y= 1-------(2)

Adding Equation 1 and 2

=> x+y+2x-y= 2+1

=> 3x= 3

=> x= 1

put X's value into equation 1

=> 1+y=2

=> y= 1

Now, mx+y= 0

put x and y into this equation

=> m(1)+1=0

=>m+1=0

=> m= -1

Hence, the value of m is -1 .

Check

mx+y= 0

-1(1)+1

=> -1+1=0

Alternative method

x+y= 2

x= 2-y-----(1)

2x-y=1

from Equation 1

=> 2(2-y)-y=1

=> 4-2y-y=1

=> 4-3y=1

=> -3y= 1-4

=> -3y= -3

y= 1

x= 2-y

x= 2-1=1

x=1

mx+y=0

m(1)+1=0

m= -1

Answer 2

Answer:

easy method and easily understand method

by substitution method

x+y=2

x=2-y 2(2-y) -y=1

4-3y=1 y=1

substitute y=1 x+1=2, x=1

now,

mx+y=0

m(1) +1=1

m=-1

hope it's help ful to all mark as brainlest answer