Question

Find the solution of this system of equations 3x+2y= -21
-7x-4y=33
help

Answer 1

The first equation given is:
3x + 2y = -21
This can be rewritten as:
2y = -21 - 3x .............> equation I

The second given equation is:
-7x - 4y = 33
This can be rewritten as:
-7x - 2(2y) = 33 ............> equation II

Substitute with equation I in equation II to get the value of x as follows:
-7x - 2(2y) = 33
-7x -2(-21-3x) = 33
-7x + 42 + 6x = 33
-x = 33-42 = -9
x = 9

Substitute with the value of x in equation I to get the value of y as follows:
2y = -21 - 3x
2y = -21 -3(9)
2y = -21-27 = -48
y = -24

Based on the above calculations:
x - 9
y = -24

Answer 2

The system is

i) 3x+2y=-21
ii) -7x-4y=33.

We notice that we can eliminate the y's by multiplying the first equation by 2, and adding this equation to the second one, as follows:

multiplying equation (i) by 2 we have

i) 6x+4y=-42
ii) -7x-4y=33.

Adding these equations side by side, we get:

6x-7x=-42+33, which simplifies to -x=-9, thus x=9.


Since 3x+2y=-21, substituting x=9, we can find y:

3(9)+2y=-21
27+2y=-21
2y=-21-27
2y=-48
thus y=-28/2=-24.

The solution of the system is (x,y)=(9, -24).