Which description does NOT guarantee that a quadrilateral is a rectangle? A a quadrilateral with all four angles right

B a parallelogram with congruent sides

C a quadrilateral with diagonals that are congruent and bisect each other

D a quadrilateral with all congruent angles

A

 a quadrilateral with all four angles right

Step-by-step explanation:

A  quadrilateral is a rectangle if a quadrilateral has all four angles right,

a parallelogram with congruent sides

a quadrilateral with diagonals that are congruent and bisect each other

a quadrilateral with all congruent angles. Because a rectangle possesses 2 pairs of parallel sides, 4 right angles at 90°. It has opposite sides which

are parallel and  congruent. And all its angles are congruent.

But a quadrilateral with all four angles right is a description that does NOT guarantee that a quadrilateral is a rectangle. Because this description is also applicable to a square.

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