Coefficient of x5 in the product (1+x2)5(1+x)4 = The coefficient of x5 in [5C0+5C1(x2)+5C2(x2)2+5C3(x2)3+5C4(x2)4+5C5(x2)5]×[4C0+4C1x+4C2x2+4C3x3+4C4x4] = The coefficient of x5 in [5C0+5C1x2+5C2x4+5C3x6+5C4x8+5C5x10]×[4C0+4C1x+4C2x2+4C3x3+4C4x4] =5C1×4C3+5C2×4C1 =5×4+10×4 =20+40=60