Someone me with these three problems, i really need to get my grade up

81=16x²+24x+9

72=8(2x²+3x)

9=2x²+3x

0=2x²+3x-9

0=(2x-3)(x+3)

X=3/2 or -3

18=36x²+12x+1

0=36x²+12x-17

x=(-12±√(144-4(36)(-17))/2(36)

X=0.54 or 0.874

28=25x²+40x+16

0=25x²+40x-12

X=(-40±√(40²-4(25)(-12))/2(25)

X=-1.858 or 0.258

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value

answer: c.  

step-by-step explanation:

mixtures containing substances that get attracted to magnet can be separated using a magnet. we can separate iron from a mixture of sand and iron, as only iron attracts to the magnet.