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第46頁(yè)

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?$ \begin{aligned} 解：原式&=16－25×(－\frac {2}{5}) \\ &=16－(－10) \\ &=26 \\ \end{aligned}$?

?$ \begin{aligned} 解：原式&=(\frac {1}{6}－\frac {2}{7}+\frac {2}{3})×(－\frac {42}{5}) \\ &=(－\frac {7}{5})+\frac {12}{5}－\frac {28}{5} \\ &=－\frac {23}{5} \\ \end{aligned}$?

?$ \begin{aligned} 解：原式&=\frac {11}{2}×(－\frac {1}{6})×\frac {3}{11}÷\frac {3}{4} \\ &=－(\frac {11}{2}×\frac {1}{6}×\frac {3}{11}×\frac {4}{3}) \\ &=－\frac {1}{3} \\ \end{aligned}$?

?$ \begin{aligned}解：原式&=－54÷9×(－\frac {1}{6})－1 \\ &=－6×(－\frac {1}{6})－1 \\ &=1－1 \\ &=0 \\ \end{aligned}$?

?$ 解：原式=(－15)×6÷(\frac {1}{3}－\frac {3}{2}－3) $?

?$=(－90)÷(－\frac {25}{6}) $?

?$=90×\frac {6}{25} $?

?$=\frac {108}{5} $?

$ \begin{aligned}? 解：原式&=\frac {1－2+3－4+...－14+15}{－2×(1－2+3－4+...－14+15)} \\ &=\frac {1}{－2} \\ &=－\frac {1}{2} \\ \end{aligned}$

$ ?$

?$ 解：(1)原式=(－5)2+(－6)+42－(－1)$?

?$=25－6+16+1$?

?$=36$?

?$(2)若－3≥x，則(－3)2－x=13$?

?$解得x=－4，符合題意$?

?$若－3＜x，則x2+(－3)=13$?

?$x2=16，x=4或x=－4(舍去)$?

?$綜上所述：x的值為4或－4$?

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第46頁(yè)