help please ! thank you !

Mapel : Matematika
Kelas : VIII SMP
Bab : Teorema Pythagoras

Pembahasan :
Berdasarkan Teorema Pythagoras
SM² = Tinggi² + Alas²
(2x + 3)² =12² + x²
4x² + 12x + 9 = 144 + x²
3x² + 12x - 135 = 0
x² + 4x - 45 = 0
(x + 9)(x - 5) = 0
x = -9 ——» TM
x = 5

Keliling = 2x + 3 + x + 12
Keliling = 3x + 15
Keliling = 3(5) + 15
Keliling = 30 cm