mohon dijawab nomor 14,15,21,25. Pake jalan nya. Dikumpul besok

14) x^2 + 2x - 35 = 0
(x + 7)(x - 5) = 0
x = -7 atau x = 5
Persamaan kuadrat yg akar-akarnya 2 kalinya :
2.x1 = 2(-7) = -14 dan
2.x2 = 2(5) = 10
adalah :
(x + 14)(x - 10) = 0
x^2 - 10x + 14x - 140 = 0
x^2 + 4x - 140 = 0

15) 5x^2 + 2x - 7 = 0
5x^2 + 2x = 7
5x^2 + 2x + .... = 7 + .....
5(x^2 + (2/5)x + ... ) = 7 + .... => (-b/2a)^2 = (-2/(2.5))^2 = (-1/5)^2 = 1/25
5(x^2 + (2/5)x + 1/25) = 7 + 5 . 1/25
5(x + 1/5)^2 = 7 + 1/5
5(x + 1/5)^2 = 36/5
(x + 1/5)^2 = 36/25

21) 2x^2 + 5x = 3
2x^2 + 5x - 3 = 0
x1 + x2 = -b/a = -5/2 = -2 1/2
x1.x2 = c/a = -3/2 = -1 1/2

25) keliling = 54
2(p + l) = 54
p + l = 27
l = 27 - p

Luas = p . l
180 = p (27 - p)
180 = 27p - p^2
p^2 - 27p + 180 = 0
(p - 15)(p - 12) = 0
p = 15 atau p = 12
Jika p = 15 => l = 27 - 15 = 12
Jika p = 12 => l = 27 - 12 = 15
Kita ambil p = 15 dan l = 12
Maka selisih panjang dan lebar = 15 - 12 = 3 cm