Question

How do you solve x+y=4 and y=x+4?

Answer 1

Answer;

$x + y = 4 ....(i)\\ y - x = 4....(ii)$

Solving for eqⁿ (i),

$x + y = 4 \\ \\ y = 4 - x$

Putting the value of y in (ii),

$y - x = 4 \\ \\ 4 - x - x = 4 \\ \\ 4 - 2x = 4 \\ \\ - 2x = 4 - 4 \\ \\ \boxed{ \fcolorbox{red}{yellow}{ \bf x = 0}}$

Substituting the value of x in (i),

$x + y = 4 \\ \\ 0 + y = 4 \\ \\ \boxed{ \fcolorbox{red}{yellow}{ \bf y = 4}}$

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