Tolong no 21 dan 25 + caranya plis !!

Bab Persamaan Kuadrat
Matematika SMP Kelas VIII

21] x² + mx - m² = 0 → salah satu akarnya adalah 2
2² + 2m - m² = 0
**pindah ruas**

m² - 2m - 4 = 0
a = 1; b = -2; c = -4

m₁₂ = (-b +- √(b² - 4 x a x c))/(2 x a)
m₁₂ = (-(-2) +- √((-2)² - 4 x 1 x (-4))) / (2 x 1)
m₁₂ = (2 +- √(4 + 16))/2
m₁₂ = (2 +- √20)/2
m₁₂ = (2 +- 2√5)/2
m₁₂ = 1 +-  √5

jawabannya D

25] ax + by = c; sejajar, (p, q)
ax + by = a . p + b . q

2y = 4x - 1
4x - 2y = 1, sejajar, (0, 8)
4x - 2y = 4 . 0 - 2 . 8
4x - 2y = -16
**dibagi 2**
2x - y = -8
y = 2x + 8

jawabannya A