Toán Lớp 8: Bài 3 : Tính nhanh:
a) 1532 + 94 .153 + 472
b) 1262 – 152.126 + 5776
c) 38.58 – (154 – 1)(154 + 1)
d) (2 + 1)(22 + 1)(24 + 1) … (220 + 1) + 1 =
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 8: Bài 3 : Tính nhanh:
a) 1532 + 94 .153 + 472
b) 1262 – 152.126 + 5776
c) 38.58 – (154 – 1)(154 + 1)
d) (2 + 1)(22 + 1)(24 + 1) … (220 + 1) + 1 =
Comments ( 1 )
a){153^2} + 94.153 + {47^2}\\
= {153^2} + 2.47.153 + {47^2}\\
= {\left( {153 + 47} \right)^2}\\
= {200^2}\\
= 40000\\
b){126^2} – 152.126 + {76^2}\\
= {126^2} – 2.76.126 + {76^2}\\
= {\left( {126 – 76} \right)^2}\\
= {50^2}\\
= 2500\\
c)38.58 – \left( {154 – 1} \right)\left( {154 + 1} \right)\\
= \left( {48 – 10} \right)\left( {48 + 10} \right) – {154^2} + 1\\
= {48^2} – {10^2} – {154^2} + 1\\
= – 21511\\
d)\left( {2 + 1} \right)\left( {{2^2} + 1} \right)\left( {{2^4} + 1} \right)…\left( {{2^{20}} + 1} \right) + 1\\
= \left( {2 – 1} \right)\left( {2 + 1} \right)\left( {{2^2} + 1} \right)\left( {{2^4} + 1} \right)…\left( {{2^{20}} + 1} \right) + 1\\
= \left( {{2^2} – 1} \right)\left( {{2^2} + 1} \right)\left( {{2^4} + 1} \right)…\left( {{2^{20}} + 1} \right) + 1\\
= \left( {{2^4} – 1} \right)\left( {{2^4} + 1} \right)…\left( {{2^{20}} + 1} \right) + 1\\
= \left( {{2^{20}} – 1} \right)\left( {{2^{20}} + 1} \right) + 1\\
= {2^{40}} – 1 + 1\\
= {2^{40}}
\end{array}$