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2 votes
Standard to vertex form -x^2-3x+8

User Vlam
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2 Answers

4 votes

F(x) = - (x-(2/3))^2 41/2 = - (x 3/2) ^2
User Neoh
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6.6k points
5 votes

The vertex form:


f(x)=a(x-h)^2+k

(h, k) - vertex


f(x)=ax^2+bx+c\\\\h=(-b)/(2a),\ k=f(h)

We have


f(x)=-x^2-3x+8\\\\a=-1,\ b=-3,\ c=8\\\\h=(-(-3))/(2(-1))=(3)/(-2)=-(3)/(2)\\\\k=f\left(-(3)/(2)\right)=-\left(-(3)/(2)\right)^2-3\left(-(3)/(2)\right)+8=-(9)/(4)+(9)/(2)+8\\\\=-(9)/(4)+(18)/(4)+(32)/(4)=(-9+18+32)/(4)=(41)/(4)\\\\Answer:f(x)=-\left(x-\left(-(2)/(3)\right)\right)^2+(41)/(4)=-\left(x+(3)/(2)\right)^2+(41)/(2)

User Neil
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6.6k points