How do you solve -3x plus y equals 7 and 5x plus 2y equals 3?

Answer 1

-3x + y = 7

5x + 2y = 3

This is solved by SIMULTANEOUS Eq'ns.

Arbitrarily decide which letter to eliminate. In this case 'y' .

To do this multiply the top eq'n by '-2'

Hence

(+)6x - 2y = -14 ( Notice the double negative multiple becomes plus(+).

5x + 2y = 3

Add the two eq'ns

11x = -11 (Notice the 'y' has been eliminated).

x = -1

When x = -1

-3(-1) + y = 7

3 + y = 7

y = 4

Hence the solution in ( x,y) form is ( -1,4).

Answer 2

A system of equations? Try elimination.

- 2(-3X + Y = 7)

5X + 2Y = 3

6X - 2Y = - 14

5X + 2Y = 3

--------------------------add

11X = - 11

X = - 1

------------Put back in equation to solve for Y

- 3(-1) + Y = 7

3 + Y = 7

Y = 4

-------------check both equations

- 3(-1) + 4 = 7

3 + 4 = 7

top checks

5(-1) + 2(4) = 3

- 5 + 8 = 3

both equations check and the system is consistent