You can put this solution on YOUR website! Solve the system.
x + 2y = –15 ----(1)X 2
–2x + 4y = 6 ----(2)
2x + 4y = -30 ----(3)(got by multiplying (1) by 2)
(2)+(3) implies
(4y +4y) =(6)+(-30)
8y = -24
y = -24/8 = -3
y=-3 in (1) implies
x+2y =-15
x+2X(-3) = - 15
x-6 = -15
x= -15+6
x=-9
Answer: x=-9 and y= -3
Verification: Putting x=-9 and y=-3 in the other equation (2)
LHS = -2x+4y = -2X(-9)+4X(-3) = +18-12 = 6 =RHS
Therefore our values are correct
Note: Why did we multiply (1) by 2 and get (3)
To equalise the coefficients of x numerically so that we can add the resulting equation (3) with (2) and get rid of x.
Why did we have to add? why not subtract?
We add when the coefficients are equal in magnitude and opposite in sign
(we subtract when the coefficients are equal in magnitude and in sign also)
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