The coordinates of 4 points are A(0,9), B(k + 1, k + 4), C(2k, k + 3) and D(2k + 2, k + 6). Find the value(s) of k if
(a) the points A, B and C are collinear,
(b) AB is parallel to CD.​

9514 1404 393

  (a) 2 or 3

  (b) -13

Step-by-step explanation:

(a) A, B, and C are collinear if there is some constant 'c' such that ...

  B - A = c(C - A)

This will give rise to two equations in 'c' and 'k'.

  (k +1, k +4) -(0, 9) = c((2k, k+3) -(0, 9))

  (k +1, k -5) = c(2k, k -6)

And the two equations are ...

  k +1 = 2ck

  k -5 = c(k -6)

From the first, we find ...

  c = (k +1)/(2k)

From the second, we find ...

  c = (k -5)/(k -6)

Equating these expressions for c gives ...

  (k +1)/(2k) = (k -5)/(k -6)

  (k +1)(k -6) = 2k(k -5) . . . . . . . multiply by 2k(k-6)

  k^2 -5k -6 = 2k^2 -10k

  0 = k^2 -5k +6 = (k -3)(k -2)

Solutions that make the factors zero are ...

  k = 3  or  k = 2

There are two values of k that make the points collinear: 2 and 3.

__

(b) AB is parallel to CD when the slopes of the lines between them are the same

  slope of AB = (k+4 -9)/(k+1 -0) = (k -5)/(k +1)

  slope of CD = ((k +6 -(k +3))/(2k +2 -2k) = 3/2

Equating these slopes and solving for k, we get ...

  (k -5)/(k +1) = 3/2

  2(k -5) = 3(k +1)

  2k -10 = 3k +3

  -13 = k

AB is parallel to CD when k = -13.

_____

The attached shows the collinear points on the red and blue lines. The points that make parallel lines are shown on the purple lines. (The purple circles correspond to points D for k=2 and 3, so are irrelevant.) Point D is not labeled with its coordinates, (-24, -7).

168

step-by-step explanation:

i am pretty sure that the answer is 168

answer: 204

step-by-step explanation:

we are told that the revenue is

x⋅(4080−10x)=−10x^2+4080x

this is a quadratic function, so to maximize it we should find the x-value of its vertex. recall that the x-value of the vertex of the parabola ax^2+bx+c is given by the formula −b/2a.

so in this case, we have a=−10 and b=4080, so the x-value of the vertex is

−b/2a= −(4080)/2(−10)=204