Factorisation 15x2+9 9x2+30x+25 36x2-60x+25 3x2-2x-1

15x²+9
= 3 × 5x² + 3×3
= 3(5x²+3)

9x²+30x+25
=(3x)²+2×5×3x+5²
=(3x+5)²

36x²-60x+25
=(6x)²-2×5×6x+5²
=(6x-5)²