Kunci Jawaban Matematika Kelas 9 SMP Latihan 5.2 Halaman 294 Nomor 2 Terbaru, Menentukan Luas Kerucut

0 = r² + 16r – 225

r_1,2 = -16 ± √16² – 4 . 1 – 225 / 2 . 1

r_1,2 = -16 ± √256 + 900 / 2

r_1,2 = -16 ± √1156 / 2

r_1,2 = -16 ± 34 / 2

r₁ = -16 + 34 / 2

r₁ = 18/2 = 9

r₂ = -16 – 34 / 2

r₂ = -50/2 = -25 (salah)

t = √s² – r²