Answer:
7. (4, -6)
8. (1, 4)
Explanation:
7.
substitution is when we use one equation to express one variable by the other, and then use that in the second equation to solve for this other variable.
with that value we go back into the first equation and solve for the first variable.
x + y = -2
x = -2 - y
4x + 2y = 4
2x + y = 2
here we use now the x = 2 - y :
2(-2 - y) + y = 2
-4 - 2y + y = 2
-4 - y = 2
-6 - y = 0
y = -6
x = -2 - -6 = -2 + 6 = 4
8.
elimination is when we transform the equations, so that after adding both equations the sum contains only one variable, for which we can then solve. and then we use that in any of the original equations to solve for the other equation.
in our case we don't need any transformation. just by adding both equations we eliminate x and can solve for y.
-5x + 6y = 19
5x - 3y = -7
------------------------
0 3y = 12
y = 12/3 = 4
now we use that in any of the original equations. e.g. the second :
5x - 3×4 = -7
5x - 12 = -7
5x = 5
x = 1