Verified answer

(3x+1)²-(x-5)²

Identité remarquable a²-b² = (a-b)(a+b)

((3x+1)-(x-5))((3x+1)+(x-5))

(3x+1-x+5)(3x+1+x-5)

(2x+6)(4x-4)

8x²-8x+24x-24

8x²+16x-24