125.
(a + 1)(a + 1) = a²+a+a+1=a^2+2a+1
(x + 1)(x + 2) = x²+2x+x+2=x^2+3x+2
(2 + y)(y + 3) = 2y+6+y²+3y=5y+6+y^2
(a + b)(a + b) = a²+ab+ab+b^2=a^2+4ab+b^2

126.
(5m + 7n)(2n + 4m) = 10mn+20m²+14n²+28mn
(12a + b)(3a + 5b) = 36a²+60ab+3ab+5b²
(2x − 3y)(2x + 3y) = 4x²+6xy-(-6xy)-(-9y)
(5m − 2n)(3n − 5m)=15mn-(-25mn)-(-6n^2)-10

129.
(8x−3)(4x+5) = 32x²+40x-(-12x)+(-15)
8x−3·4x+5 = 32x²+40x-(-12x)+(-15)
(4a − 3) · 2a − 3 = 8a²-6a-3
4a − 3 (2a − 3) = 4a-6a+9

136.
2x+2y = 2x+2y
6a−3 = 6a-3
ax−ab = a²x-b
2a+6ab = 10ab