Evaluate
21-21a^{2}
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21-21a^{2}
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4a^{2}-20a+25-\left(5a-2\right)^{2}
Use binomial theorem \left(p-q\right)^{2}=p^{2}-2pq+q^{2} to expand \left(2a-5\right)^{2}.
4a^{2}-20a+25-\left(25a^{2}-20a+4\right)
Use binomial theorem \left(p-q\right)^{2}=p^{2}-2pq+q^{2} to expand \left(5a-2\right)^{2}.
4a^{2}-20a+25-25a^{2}+20a-4
To find the opposite of 25a^{2}-20a+4, find the opposite of each term.
-21a^{2}-20a+25+20a-4
Combine 4a^{2} and -25a^{2} to get -21a^{2}.
-21a^{2}+25-4
Combine -20a and 20a to get 0.
-21a^{2}+21
Subtract 4 from 25 to get 21.
4a^{2}-20a+25-\left(5a-2\right)^{2}
Use binomial theorem \left(p-q\right)^{2}=p^{2}-2pq+q^{2} to expand \left(2a-5\right)^{2}.
4a^{2}-20a+25-\left(25a^{2}-20a+4\right)
Use binomial theorem \left(p-q\right)^{2}=p^{2}-2pq+q^{2} to expand \left(5a-2\right)^{2}.
4a^{2}-20a+25-25a^{2}+20a-4
To find the opposite of 25a^{2}-20a+4, find the opposite of each term.
-21a^{2}-20a+25+20a-4
Combine 4a^{2} and -25a^{2} to get -21a^{2}.
-21a^{2}+25-4
Combine -20a and 20a to get 0.
-21a^{2}+21
Subtract 4 from 25 to get 21.
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Limits
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