$\left( 10x+5 \right) \times \left( 10x+5 \right)$
Multiply each term in the first parentheses by each term in the second parentheses (FOIL)$10x \times 10x+10x \times 5+5 \times 10x+5 \times 5$
Calculate the product$100{x}^{2}+10x \times 5+5 \times 10x+5 \times 5$
Calculate the product$100{x}^{2}+50x+5 \times 10x+5 \times 5$
Calculate the product$100{x}^{2}+50x+50x+5 \times 5$
Multiply the numbers$100{x}^{2}+50x+50x+25$
Collect like terms$100{x}^{2}+100x+25$