Chapter 4 - Sections 4.1-4.3 - Integrated Review - Systems of Linear Equations - Page 234: 7

$(2,-1)$

$x+y = 1 $ Equation $(1)$ $x-2y=4 $ Equation $(2)$ Solving by elimination method. Multiply Equation $(1)$ by $2$ $2x+2y = 2$ Equation $(3)$ Add Equation $(3)$ and Equation $(2)$ to eliminate $y$ $2x+x+2y-2y = 2+4$ $3x=6$ $x= 2$ Substituting $x$ value in Equation$(1)$, we get $x+y = 1 $ $2+y = 1 $ $y = 1 -2$ $y = -1$ Solution: $(2,-1)$