-8x+4y=28 solve for y

2 answers:

8 0

This is how I would do it:
-8x=28-4y divide the entire equation by 4
-2x=7-y Put y back on the left and put x on the right
y=7-2x.

mina [271]3 years ago

7 0

-8x+4y=28 You need to subtract -8x from both sides leaving:
4y=8x+28 From here you need to divide by 4 on both sides leaving:
y= 8x+28/4 Simplify:
y=2x+7

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Question 101 points)

maw [93]

Answer:

$\large\boxed{y=-\dfrac{2}{3}x+\dfrac{13}{3}}$

Step-by-step explanation:

$\text{The slope-intercept form of an equation of a line:}\\\\y=mx+b\\\\m-slope\\b-y-intercept\\\\\text{The formula of a slope:}\\\\m=\dfrac{y_2-y_1}{x_2-x_1}\\\\===============================$

$\text{We have the point:}\\\\(5,\ 1)\ \text{and}\ (-4,\ 7).\ \text{Substitute:}\\\\m=\dfrac{7-1}{-4-5}=\dfrac{6}{-9}=-\dfrac{6:3}{9:3}=-\dfrac{2}{3}\\\\\text{We have the equation in form:}\\\\y=-\dfrac{2}{3}x+b\\\\\text{Put the coordinates of the point (5, 1) to the equation:}\\\\1=-\dfrac{2}{3}(5)+b\\\\1=-\dfrac{10}{3}+b\qquad\text{add}\ \dfrac{10}{3}\ \text{to the both sides}\\\\\dfrac{3}{3}+\dfrac{10}{3}=b\to b=\dfrac{13}{3}\\\\\text{Finally:}\\\\y=-\dfrac{2}{3}x+\dfrac{13}{3}$