Evaluate
x^{2}+19x+21
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x^{2}+19x+21
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x^{2}+10x+25+9\left(x+0\right)-4
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(x+5\right)^{2}.
x^{2}+10x+25+9x-4
Anything plus zero gives itself.
x^{2}+19x+25-4
Combine 10x and 9x to get 19x.
x^{2}+19x+21
Subtract 4 from 25 to get 21.
x^{2}+10x+25+9\left(x+0\right)-4
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(x+5\right)^{2}.
x^{2}+10x+25+9x-4
Anything plus zero gives itself.
x^{2}+19x+25-4
Combine 10x and 9x to get 19x.
x^{2}+19x+21
Subtract 4 from 25 to get 21.
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