need help!

[soft harbor]

The parabola y=-x^2+bx+c intersects the line y=kx at the points (0;0) and (-4;-12). Find k, b, c.

[soft harbor]

Doesn't k = y2-y1/ x2-x1?

And c equals to 0 right

[cyan surge]

Well, this one is pretty easy imo. For c, just substitute (0,0) and get c=0

Then

Using y=kx, find k=3 by subbing in (-4,-12)

Since the parabola cuts the origin point, it can be written in the form of x²+cx

Where c is some real number

Finally, just use the (-4,-12) coordinate in the parabolic equation

simplify to get an expression like 4b=16-12

And get b=1

hope that solves it

[soft harbor]

Can you elaborate this part?

I don't get the "subbing in" part

Like

-12/-4?

[cyan surge]

the question is basically saying that in the equation y=kx, the value of y is -12 when the value of x is -4

so substitute their values

-12=k(-4)

[soft harbor]

Ohhhhhhhhhhh

Oh my god that makes so much sense

[cyan surge]

ur welcome

[soft harbor]

Ty

@cyan surge btw, is this method also acceptable?

[cyan surge]

Is that a + sign before b?

[soft harbor]

It's y=kx+b

I just slapped k and x in it

And y

Like y=-12

x= -4

[cyan surge]

Unfortunately no its unacceptable

[soft harbor]

Damn.

[cyan surge]

Because of the plus sign between b and -12

you cant divide the left side with -12, and not divide b with -12

i think the easiest approachh would be to try substituting values from both coordinates into each equation separately

That would be acceptable

[soft harbor]

I'll just do the parabolic equation

Ty

Imma close the thing now