($12x^2y - 6x^2y + 18x^2y = $)

($x^2 + 10x + 25 = ( + )^2$)

($x^2 - 25 = ( + )( - )$)

($x^2 - 6x + 8 =$)

($a^2 - 6a + 9 =$)

($x^2 - 100 =$)

($x^2 - 2x - 24 =$)

($25a^3b^2 - 15a^2b - 5ab =$)

($81x^2 - 9y^2 =$)

($16x^2 + 24x + 9 =$)

($a^2 - 3a - 40 =$)

($x^2/36 - 81 =$)

($x^2 - 2x - 15 =$)

($21x^3y^3 - 7xy + 49xy^2 =$)

($4x^2 + 12xy + 9y^2 =$)

($x^2 - 6x + 5 =$)

($25x^2 - 16y^2 =$)

($x^2 + 8x + 15 =$)

($9a^2 + 6a + 1 =$)

($6x^3y - 12xy^2 =$)

($a^2 + 3a - 18 =$)

($x^2 - y^2 =$)

($a^2 - 2a - 15 =$)

($x^2 + 5x + 4 =$)

($x^2/9 + 1/3x + 1/4 =$)