3x + y = 9 (I)
y = –4x + 10 (II)
------------------------
[tex] \left \{ {{3x + y = 9 } \atop {y = -4x + 10 }} \right. [/tex]
Pass the incognito "4x" to the first term, changing the signal when changing sides.
-------------------------
simplify by (-1)
[tex]\left \{ {{3x + y = 9.(-1)} \atop {4x + y = 10 }} \right. [/tex]
-------------------------
[tex] \left \{ {{- 3x - \diagup\!\!\!\!y =-9} \atop {4x + \diagup\!\!\!\!y = 10}} \right.
[/tex]
-------------------------
[tex] \left \{ {{- 3x = - 9} \atop {4x = 10}} \right. [/tex]
-----------
[tex]\boxed{x = 1}[/tex]
Substitute in equation (I) to find the value of "Y".
3x + y = 9 (I)
3*(1) + y = 9
3 + y = 9
y = 9 - 3
[tex]\boxed{y = 6}[/tex]
Answer:
[tex]\boxed{\boxed{ \left \ {{x=1} \atop {y=6}} \right. }}[/tex]
