a.(x+y)² = x² + 2xy + y²
b.(a+t)² = a² + 2at + t²
c.(x+2)² = x² + 2x * 2 + 2² = x² + 4x + 4
d.(b+3)² = b² + 2b * 3 + 3² = b² + 6b + 9
e.(a+5)² = a² + 2a * 5 + 5² = a² + 10a + 25
f.(3+t)² = 9 + 6t + t² = t² + 6t + 9
g.(4+m)² = m² + 8m + 16
h.(9+a)² = a² + 18a + 81
i.(y+20)² = y² + 2y * 20 + 20² = y² + 40y + 400
j.(3x+2y)² = (3x)² + 2*3x*2y + ( 2y)² = 9x² + 12xy + 4y²
k.(3+5x)² = 9 + 30x + 25x² = 25x² + 30x + 9