Toán Lớp 6: So sánh
a,A = 2019.2021 và B = 20202.
b, A=2^ 0 +2^ 1 +2^ 2 +2^ 3 +…+2^ 2020 và B=2^ 2021 -1
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Toán Lớp 6: So sánh
a,A = 2019.2021 và B = 20202.
b, A=2^ 0 +2^ 1 +2^ 2 +2^ 3 +…+2^ 2020 và B=2^ 2021 -1
Comments ( 1 )
a)A = 2019.2021\\
= \left( {2020 – 1} \right)\left( {2020 + 1} \right)\\
= {2020^2} – 1 < {2020^2}\\
\Leftrightarrow A < B\\
b)\\
A = {2^0} + {2^1} + {2^2} + …. + {2^{2020}}\\
\Leftrightarrow 2A = {2^1} + {2^2} + {2^3} + … + {2^{2021}}\\
\Leftrightarrow 2A – A = {2^{2021}} – {2^0}\\
\Leftrightarrow A = {2^{2021}} – 1\\
\Leftrightarrow A = B
\end{array}$