Bài 156 trang 64 SGK Toán 6 tập 2

Rút gọn:

a) \(\displaystyle {{7.25 - 49} \over {7.24 + 21}}\)

b) \(\displaystyle {{2.\left( { - 13} \right).9.10} \over {\left( { - 3} \right).4.\left( { - 5} \right).26}}\)

Lời giải

a) \( \displaystyle {{7.25 - 49} \over {7.24 + 21}} = {{7.25 - 7.7} \over {7.24 + 7.3}}\)\(\displaystyle ={{7(25 - 7)} \over {7(24 + 3)}} = {{18} \over {27}} = {2 \over 3}\)

b)  \( \displaystyle {{2.\left( { - 13} \right).9.10} \over {\left( { - 3} \right).4.\left( { - 5} \right).26}} \)\(\displaystyle = {{2( - 13).3.3.2.5} \over {( - 3).2.2( - 5).13.2}} = {{ - 3} \over 2}\)


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