Use the geometric mean for right triangles here. Like this

. Cross multiply to get

, and

. That simplifies down to

. Pull out the 9 as a perfect square of 3 and you're left with

, first choice above.
It would be
, or, in simplest form,
.
You get this by adding all the marbles to find the total number of marbles. <em>10+7+12+9</em>, which equals <em>38</em>.
You have <u>10 red marbles out of 38 total</u>, so that is represented by
!
-4 would be the correct answer to the problem
I think it is c. Hope this helps!
Answer:
(-7,4)
Step-by-step explanation:
goal: (y-k)^2=4p(x-h)
y^2-8y=4x+12 Rearranged and added 4x and 12 on both sides
y^2-8y+(-8/2)^2=4x+12+(-8/2)^2 complete square time (add same thing on both sides)
y^2-8y+(-4)^2=4x+12+(-4)^2 (simplify inside the squares)
(y-4)^2=4x+12+16 (now write the left hand side as a square)
(y-4)^2=4x+28
(y-4)^2=4(x+7) factored...
vertex is (-7,4)