Question

com faz issa (A+3x)2

Answer 1

(A + 3x) . (A + 3x)
A^2 + 3xA + 3xA + 9x^2
A^2 + 6xA + 9x^2

Answer 2

$(a + 3x) (a + 3x) \\ \\ a^2 + 3ax + 3ax + 9x^2 \\ \\ => \ a^2 + 6ax + 9x^2$