8 cm the answer is hope it helps good luck
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Question:
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6 - (-8) = 6 + 8 = 14
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Options :
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A) -6 + 8 = 2
B) - 6 + - 8 =-6 - 8 . = -14
C) 6 + -8 = 6 - 8 = -2
D) 6 + 8 = 14 (Answer)
Since x term is squared, solve for form (x-h)^2=4p(y-k)
x term is squraed so it opens down or up
vertex is (h,k)
p is distance from vertex to focus and from vertex to directix
if p>0, then dirextix is below vertex
if p<0, directix is above vertex
complete the square
y=(-1/6x^2+7x)-80
y=(-1/6)(x^2-42x)-80
take 1/2 of linear coefient and squer it and add negative and positive inside
-42/2=-21, (-21)^2=441
y=(-1/6)(x^2-42+441-441)-80
factor perfect square the square
y=(-1/6)((x-21)^2-411)-80
expand
y=(-1/6)(x-21)^2+73.5-80
y=(-1/6)(x-21)^2-6.5
add 6.5 to both sid
y+6.5=(-1/6)(x-21)^2
times both sides by -6
-6(y+6.5)=(x-21)^2
(x-21)^2=-6(y+6.5)
(y-21)^2=4(-3/2)(y-(-6.5))
vertex is
-3/2<0 so directix is above
it is -3/2 or 1.5 units above the vertex
up is y so
-6.5+1.5=-5
the directix is y=-5
-6x+3=45
-3 -3 subtract
-6x=45
Divide both sides by -6
X=-7
I think this is the answer