A caterpillar crawling in a straight line across a coordinate plane starts at point (-3, -4) and ends at point (25, 38). Counting the start point and end point, how many
points with integer coordinates does the caterpillar touch?

9514 1404 393

  15

Step-by-step explanation:

In vector form, the equation of point p on the line can be written as ...

  p = (-3, -4) +t(25 -(-3), 38 -(-4)) . . . . . for some scalar t

  p = (-3, -4) +t(28, 42)

  p = (-3, -4) +14t(2, 3)

where t takes on any value between 0 and 1.

If we let t = n/14 for some integer 0 ≤ n ≤ 14, then the coordinates of point p will be integers.

There are 15 values that n can have in the allowed range.

The caterpillar touches 15 points with integer coordinates.

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