Question

-3x + 2y = 21 -4x + y = 23

Answer 1

Answer: x=-5 and y=3

Step-by-step explanation:

-3x + 2y = 21 ............ Eq 1

-4x + y = 23 .............. Eq2

In eq 2,let's make y the subject of the formula ; add 4x to both sides to get : - 4x + 4x + y = 23 + 4x

Which gives: y = 23 + 4x .... Eq3

Put this value of y into eq 1 to get;

-3x + 2(23 + 4x) = 21

Which gives: - 3x + 46 + 8x = 21

Which givea; 5x + 46 = 21

Subtract 46 from both sides to get;

5x + 46 - 46 = 21 - 46 to get

5x = - 25

Divide both sides by 5;

5x/5 = - 25/5

Therefore, x = - 5

Now,put - 5 for x in Eq3;

y = 23 + 4(-5)

y = 23 - 20

y = 3

Therefore the solution to the question is x=-5 and y=3

Answer 2

Answer:

2y = 3x + 21

y = 1.5x + 10.5

plug in, in the second equation

- 4x + (1.5x + 10.5) = 23

-4x + 1.5x + 10.5 = 23

-2.5x + 10.5 = 23

-2.5x = 12.5

x = 12.5/-2.5 = -5

y = 1.5 (-5) + 10.5 = 3

x = -5

y = 3