Question

Substitution: y-2x=-6 and 5x-y=9

Answer 1

`\left \{ {\big{y-2x=-6} \atop\big {5x-y=9\ \ }} \right. \\\\ \left \{ {\big{y=2x-6\ \ \ \ \ \ \ \ \ \ } \atop\big {5x-(2x-6)=9\ \ }} \right. \\\\ \left \{ {\big{y=2x-6\ \ \ \ \ \ \ \ \ \ } \atop\big {5x-2x+6=9\ \ }} \right. \\\\ \left \{ {\big{y=2x-6\ \ } \atop\big {3x=3\ /:3 }} \right. \\\\ \left \{ {\big{y=2x-6 } \atop\big {x=1\ \ \ \ \ \ }} \right. \\\\ \left \{ {\big{y=-4 } \atop\big {x=1\ }} \right. \\\\`


`Ans.\ \left \{ {\big{x=1} \atop\big {y=-4}} \right. \ \ \ \Rightarrow\ \ \ point:\ \ (1;-4)`

Answer 2

y-2x=-6 and 5x-y=9

step 1: isolate y in the first equation

y = 2x - 6

step 2: substitute the y value on the 2th equation:

5x-(2x-6)=9

step 3: solve the present equation:

5x - 2x + 6 = 9
3x = 9-6
3x = 3
x = 1

step 4: get the y value by replacing the value of x in y = 2x - 6:

y = 2*1 - 6
y = 2 - 6
y = -4

S={1, -4}