Which of the following are possible ways to eliminate a variable by multiplying first? x + 2y = 1
4x - 7y = 0

A. Multiply the first equation by 7 and the second equation by 2

B. Multiply the second equation by 4

C. Multiply the first equation by 4 and the second equation by 2

D. Multiply the first equation by 4

E. Multiply the first equation by 2 and the second equation by 7

F. Multiply the first equation by 7 and the second equation by 4

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step-by-step explanation:

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.

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step-by-step explanation:

step-by-step explanation: