How do you solve the equation for y, given $y + 7 x = 9$ $y+7x=9$ then find the value for each value of x: -1, 0, 4?

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Answer 1 · 2016-11-01T08:36:10

$(- 1, 16) (0.9) (4, - 19)$ $(-1, 16)" "(0.9)" "(4, -19)$

$y + 7 x = 9$ $y+7x = 9$

There are 2 variables in this equation, which means that you can't solve it and find ONE unique solution. There are infinitely many solutions.

"Solve for y" means write the equation as $y = ..........$

$y +7x -7x = 9 -7x" "larr$ subtract $7x$ from each side

$" "y = -7x+9" "larr$ equation of a straight line

Now you have been given various values of $x$ . Use each in turn in the equation and find the corresponding values of $y$

$" "y = -7color(magenta)(x)+9$

$color(magenta)(x =-1) rarr" " y = -7color(magenta)((-1)) +9$
$color(white)(xxxxxx.xxxxx)y = +7+9 = 16$

$color(magenta)(x =0) rarr" " y = -7color(magenta)((0)) +9$
$color(white)(xxxxxx..xxxx)y = 0+9 = 9$

$color(magenta)(x =4) rarr" " y = -7color(magenta)((4)) +9$
$color(white)(xxxxxx...xxxx)y = -28+9 = -19$

What you have actually found is three points, $(x, y)$ on a line.
$(-1, 16)" "(0.9)" "(4, -19)$

How do you solve the equation for y, given y+7x=9y+7x=9y+7x=9 then find the value for each value of x: -1, 0, 4?