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Which point gives the vertex of ƒ(x) = –x2 + 4x – 3?

Which point gives the vertex of ƒ(x) = –x2 + 4x – 3?-example-1
User Xhg
by
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1 Answer

4 votes

Answer:

The vertex is (2,1)

Explanation:

ƒ(x) = –x^2 + 4x – 3

Factor out the negative

= -(x^2 -4x+3)

Factor

What 2 numbers multiply to +3 and add to -4

-3*-1 = 3

-3+-1 = -4

f(x) = -( x-3)(x-1)

Find the zeros

0 = -( x-3)(x-1)

0 = x-3 0 = x-1

x=3 x=1

The x value of the vertex is 1/2 way between the two zeros

(3+1)/2 = 4/2 =2

To find the y value, substitute x=2 in

f(2) = -( 2-3)(2-1)

=-(-1)(1) = 1

The vertex is (2,1)

User Pramodtech
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6.7k points