a) \(85^2-15^2=\left(85-15\right)\left(85+15\right)=70.100=7000\)
b) \(93^3+21.93^2+3.49.93+343\)
\(=93^3+3.7.93^2+3.7^2.93+7^3\)
\(=\left(93+7\right)^3\)
\(=100^3=1000000\)
c) \(73^2-13^2-10^2+20.13\)
\(=73^2-\left(13^2+10^2-20.13\right)\)
\(=73^2-\left(13-10\right)^2\)
\(=73^2-3^2\)
\(=\left(73+3\right)\left(73-3\right)\)
\(=76.70=5320\)
d) Viết = Latex hộ mình
a) Ta có: \(85^2-15^2\)
\(=\left(85-15\right)\left(85+15\right)\)
\(=70\cdot100=7000\)
b) Ta có: \(93^3+21\cdot93^2+3\cdot49\cdot93+343\)
\(=93^3+3\cdot93^2\cdot7+3\cdot93+7^2+7^3\)
\(=\left(93+7\right)^3\)
\(=100^3=1000000\)
c) Ta có: \(73^2-13^2-10^2+20\cdot13\)
\(=73^2-\left(13^2+10^2-20\cdot13\right)\)
\(=73^2-\left(13^2-2\cdot13\cdot10+10^2\right)\)
\(=73^2-\left(13-10\right)^2\)
\(=73^2-3^2=\left(73-3\right)\left(73+3\right)\)
\(=70\cdot76=5320\)
