Question

Find the equation of the line tangent to y = –3x2 + x – 5 at x = –1.

Answer 1

first find the derivative dy/dx

Answer 2

can you do that?

Answer 3

Would it be -6x+1?

Answer 4

yes

so plug in x = -1 at this will give you the slope of the tangent

Answer 5

* and this

Answer 6

So the slope of the tangent line would be 7 right?

Answer 7

yes

Answer 8

now you need to use the general form

y - y1 = m(x - x1)

where m = 7 and (x1,y1) is a point on the line

use x1 = -1 and find y1 by substituting in the equation of the curve.

Answer 9

Would it be 2?

Answer 10

Would 7x-2 be my answer?

Answer 11

for y1?
no

y1 = -3(-1)^2 - 1 - 5

Answer 12

Oh you get -9

Answer 13

y -(-9) = 7(x -(-1))
y + 9 = 7x + 7
y = 7x - 2

Answer 14

Okay thank you!

Answer 15

yw