Grafik fungsi kuadrat berbentuk parabola.
Untuk menggambarkan grafik fungsi kuadrat yang memotong sumbu-
di titik
dan
serta memotong sumbu-
di titik
, titik balik dari fungsi tersebut perlu diketahui.
Untuk mencari titik balik dari fungsi kuadrat, persamaan fungsi kuadrat akan dicari terlebih dahulu.
Oleh karena dua titik potong sumbu-
diketahui, yaitu
dan
, maka persamaan fungsi kuadrat dapat dinyatakan sebgai berikut
![y equals a open parentheses x plus 4 close parentheses open parentheses x minus 3 close parentheses](data:image/png;base64,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)
Nilai
pada persamaan di atas, akan dicari dengan menyubtitusi nilai titik potong pada sumbu-
ke persamaan di atas, yaitu
, sehingga diperoleh
Dengan menyubtitusi nilai
ke persamaan di atas, diperoleh persamaan fungsi kuadrat pada soal adalah
Dari persamaan fungsi kuadrat di atas yang mempunyai bentuk umum
, diperoleh nilai absis untuk titik balik fungsi kuadrat di atas adalah
![x equals fraction numerator negative b over denominator 2 a end fraction equals fraction numerator negative 1 over denominator 2 open parentheses 1 close parentheses end fraction equals negative 1 half](data:image/png;base64,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)
dan dengan menyubtitusi nilai absis yang diperoleh ke persamaan fungsi kuadrat di atas, diperoleh nilai ordinat untuk titik balik fungsi kuadrat di atas adalah
![table attributes columnalign right center left columnspacing 0px end attributes row y equals cell open parentheses negative 1 half close parentheses squared plus open parentheses negative 1 half close parentheses minus 12 end cell row blank equals cell 1 fourth minus 1 half minus 12 end cell row blank equals cell negative 12 1 fourth end cell end table](data:image/png;base64,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)
Dengan demikian, diperoleh titik balik dari fungsi kuadrat pada soal adalah
.
Dengan menggambarkan titik-titik potong sumbu-
,
dan
, titik potong sumbu-
,
, dan titik balik fungsi,
, pada suatu bidang Cartesius dan lalu menghubungkan titik-titik tersebut sehingga menjadi kurva mulus, diperoleh grafik fungsi kuadrat sebagai berikut:
![](https://imgix2.ruangguru.com/assets/miscellaneous/png_wrvasp_9148.png)