Which value can be used as the common ratio in an explicit formula that represents the sequence? One-half 2 6 12

Step-by-step explanation:

The common ratio is the current number divided by the previous. So the ratio is 1/2

The sequence is 12, 6, 3, 3/2, 3/4 ...

You can obtain any number multiplying the previous number times 1/2.

6 = 12 *(1/2)

3 = 6*(1/2)

3/2 = 3*(1/2)

3. parallelogram

step-by-step explanation:

we turn each of our sides into direction vectors

ab=b-a=(3 - 7, 1 - 0) = (-4, 1)

bc=c-b=(1,6)

cd=d-c=(4,-1)

da=a-d=(-1,-6)

we see how the opposite sides have negated direction vectors; this is characteristic of a parallelogram.   we have congruent sides ab=cd and bc=da with unequal lengths because 1^2+6^2 is different from (-4)^2+1^2.   so it's not a square or a rhombus.  

we check the dot product of direction vectors of adjacent sides.   we have

ab dot bc = -4(1) + 1(6) = 2

that's not zero so the sides are not perpendicular.   we've ruled out rectangle.

the direction vectors indicate two pairs of congruent parallel sides, so we choose parallelogram over trapezoid.

phosphate, calcium ion, chloride ion, neon atom

step-by-step explanation: