Help!!

y = x^2 -3x + 4      (1)

x + y  = 4  ⇒   y  = 4 - x    (2)

Sub (2)  into (1)

4 - x  =  x^2  - 3x + 4       subtract 4 from both sides

-x = x^2 - 3x       add x to both sides

x^2 - 2x  = 0   factor

x( x - 2)  =  0

Set each factor to 0 and solve for x and we get that

x =  0   or x  = 2

When x = 0.....y  =  4 - 0  =    4      ⇒   (0, 4)

When x  =  2.....y  =  4 -  2   =  2  ⇒    (2 , 2)