Bài 35 trang 17 SGK Toán 8 tập 1

Tính nhanh:

\(\eqalign{
& a)\,\,{34^2} + {66^2} + 68.66 \cr
& b)\,\,{74^2} + {24^2} - 48.74 \cr} \)

Lời giải

\(\eqalign{
& a)\,\,{34^2} + {66^2} + 68.66 \cr
& = {34^2} + 68.66 + {66^2} \cr
& = {34^2} + 2.34.66 + {66^2} \cr
& = {\left( {34 + 66} \right)^2} \cr
& = {100^2} = 10000 \cr} \)

\(\eqalign{
& b)\,\,{74^2} + {24^2} - 48.74 \cr
& = {74^2} - 48.74 + {24^2} \cr
& = {74^2} - 2.74.24 + {24^2} \cr
& = {\left( {74 - 24} \right)^2} \cr
& = {50^2} = 2500 \cr} \)


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