Answer
$x^{20}+40x^{14}y+760x^{18}y^{2}$
Work Step by Step
$\left( x+2y\right) ^{20}=\binom {20}{0} \times x^{20} \times y^{0}+\binom {20}{1} \times x^{19} \times y^{1} +\binom {20}{2} \times x^{18} \times y^{2} \dots =\dfrac {20!}{0!\left( 20-0\right) !}\times x^{20}\times \left( 2y\right) ^{0}+\dfrac {20!}{1!\left( 20-1\right) !}\times x^{19 }\times \left( 2y\right) ^{1}+\dfrac {20!}{2!\left( 20-2\right) !}\times x^ {18}\times \left( 2y\right) ^{2} \dots ==x^{20}+20\times x^{19}\times \left( 2y\right) +190\times x^{18}\times \left( 2y\right) ^{2}=x^{20}+40x^{14}y+760x^{18}y^{2} \dots $
