# f4 maths (1 quesion)

f(x)=-3x2-2x+1

找這三個:

the line of symmetry

the vertex

the y-intercept

### 1 Answer

Rating

- Yin FaiLv 61 decade agoFavorite Answer
f(x) = -3x2 - 2x + 1

y-intercept = f(0) = +1

Use completing square method,

f(x) = -3 (x2 + 2x/3) + 1

= -3 (x2 + 2x/3 + 1/9 - 1/9) + 1

= -3 (x2 + 2x/3 + 1/9) + 1/3 + 1

= -3 (x2 + 2x/3 + 1/9) + 4/3

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

Line of symmetry : x = -1/3

vertex = (-1/3, 4/3)

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