Need asap! 10 pts!
solve each system by elimination.
1. -9x+2y= -1.
18x-7y=17

2. 4x+18y= -28
2x+9y= -14

3. 20x+y= -11
-10x-3y= -17

4. -3x+y=7
-6x+2y=12

you!

Problem 1
-9x + 2y = -1             (1)
18x - 7y = 17             (2)
To eliminate x, multiply (1) by 2 to obtain
-18x + 4y = -2
 18x - 7y = 17
Add the two equations.
-3y = 15
y = -5
From (2), obtain
18x = 17 + 7y = 17 + 7*(-5) = -18
x = -1

 x= -1, y = -5

Problem 2.
4x + 18y = -28           (1)
2x + 9y = -14             (2)
Divide (1) by 2 to obtain the system of equations
2x + 9y = -14
2x + 9y = -14
These two equations re identical.
Therefore there are an infinite number of solutions.

There is no unique set of solutions.

Problem 3.
 20x + y = -11           (1)
-10x - 3y = -17         (2)
Multiply (2) by 2 to obtain
 20x + y = -11
-20x - 6y = -34
Add the two equations to eliminate x.
-5y = -45
y = 9
From (1), obtain
20x = -11 - y = -11 - 9 = -20
x = -1

 x = -1,  y = 9

Problem 4
-3x + y = 7           (1)
-6x + 2y = 12       (2)
Divide (2) to obtain the system of equations
-3x + y = 7
-3x + y = 6
Because 7 ≠ 6, th set of equations is nonsensical (inconsistent).

The set of equations is invalid, and it has no solution.