182k views
15 votes
A student writes the equation for a line that has a slope

of -6 and passes through the point (2, -8).
y--8) = -6(x - 2)
y-(-8) = -6x + 12
Y-(-8) + 8 = -6x + 12 + 8
y = -6x + 20
MA
Explain why the work is not correct.

2 Answers

2 votes
y = mx + c
Where
y is the y of (2, -8)
x is the x of (2, -8)
m is the gradient or slope
c is the y intercept (you don’t know what it is)

Put into equation and find c

Once find c rewrite the equation with only the m and c in numbers

Eg

y = 5x + 3 (this is an example not the answer)

Hope this is helpful if you don’t understand please comment
User M D
by
8.5k points
9 votes
Answer: the student is incorrect.

Point slope form: y - y1 = m (x - x1)
Used when given one point and a slope (m)

(2, -8) and a slope of -6
y - y1 = m (x - x1)
y - (-8) = -6(x - 2)
y + 8 = -6x + 12
- 8 - 8
y = -6x + 4

Check your answer using (2, -8):
y = -6x + 4
-8 = -6(2) + 4
-8 = -12 + 4
- 8 = -8
This statement is true.


Another way to explain why they are incorrect:
y - (-8) = -6(x - 2)
y + 8 = -6x + 12 (This is where they went wrong. Two negatives next to each other when subtracting, make a positive)
y + 8 = -6x + 12
- 8 - 8
y = -6x + 4


Hope this helps!
User Gammer
by
8.5k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories