The graph of the function f(x) = (x - 3)(x + 1) is shown.
which describes all of the values for which the graph is
positive and decreasing?

Step-by-step explanation:

Option A. All the real values of x where x < -1

Procedure

Solve the inequality:

(x -3)(x+1)>0

That happens in two cases.

1) When both factors >0

x-3>0 and x+1>0

x>3 and x >-1

The intersection is x >3

2) When both factors <0

x-3<0 and x+1<0

x<3 and x<-1

the intersection is x<-1.

We have obtained that the function is positive for the intervals  x < -1 and x > 3. But in one of those intervals the function is decresing and in the other is increasing.

You can recognize that the function given is a parabola and, because the coefficient of the quadratic term is positive, the parabola opens upward. Then the function is decreasing in the  first interval and increasing in the second interval.

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12

6 cm

step-by-step explanation: