Which is a recursive formula for the sequence 99.4, 0, –99.4, –198.8, where f(1) = 99.4?

f(x)= -99.4x + 198.8

f(1) = -99.4*1 + 198.8 = 99.4

f(2) = -99.4*2 + 198.8 = 0

f(3) = -99.4*3 + 198.8 = -99.4

f(4) = -99.4*4 + 198.8 = -198.8

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.

step-by-step explanation: