Buatlah sketsa grafik fungsi kuadrat dengan caranya F(x)= x²+4x-21

<p>f(x) = x² + 4x - 21<br>karena a&gt;0, maka grafik terbuka ke atas seperti huruf &nbsp;U<br>a=1, b =4, c=-21<br>a) titik potong dengan sumbu y maka x = 0, subtitusi ke dalam persamaan<br>x = 0 maka y = -21 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(0,-21)<br>b) titik potong dengan sumbu x, maka y = 0, subtitusi ke dalam persamaan<br>x² + 4x - 21 = 0 (faktorkan)<br>(x+7) (x-3) = 0<br>x = -7 V x = 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; (-7,0) dan (3,0)<br>c) titik puncak<br>x = -b/2a = -4/2(1) = -2, subtitusi nilai x ke dalam persamaan<br>y &nbsp;= (-2)² + 4(-2) - 21 = 4 -8 - 21=-25<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(-2, -25)<br><br>gambar menggunakan titik-titik yang sudah diketahui, kira-kira seperti gambar berikut</p>