Toán Lớp 7: 1) tính:
a,-5 mũ 60 x 30 mũ 5 /15 mũ 5 x 5 mũ 61
b,(1/3) mũ 2 – (-12/17) mũ 0 +(-1/2) mũ 3 x 4 mũ 2
2) chứng minh :
a,(7 mũ 6 +7 mũ 5 -7 mũ 4) chia hết cho 11
b,(10 mũ 9 + 10 mũ 8 + 10 mũ 7 ) chia hết cho 222
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Toán Lớp 7: 1) tính:
a,-5 mũ 60 x 30 mũ 5 /15 mũ 5 x 5 mũ 61
b,(1/3) mũ 2 – (-12/17) mũ 0 +(-1/2) mũ 3 x 4 mũ 2
2) chứng minh :
a,(7 mũ 6 +7 mũ 5 -7 mũ 4) chia hết cho 11
b,(10 mũ 9 + 10 mũ 8 + 10 mũ 7 ) chia hết cho 222
Comments ( 1 )
1,\\
a,\\
\dfrac{{{{\left( { – 5} \right)}^{60}}{{.30}^5}}}{{{{15}^5}{{.5}^{61}}}} = \dfrac{{{5^{60}}.{{\left( {5.2.3} \right)}^5}}}{{{{\left( {3.5} \right)}^5}{{.5}^{61}}}}\\
= \dfrac{{{5^{60}}{{.5}^5}{{.2}^5}{{.3}^5}}}{{{3^5}{{.5}^5}{{.5}^{61}}}} = \dfrac{{{5^{65}}{{.2}^5}{{.3}^5}}}{{{3^5}{{.5}^{66}}}} = \dfrac{{{2^5}}}{5} = \dfrac{{32}}{5}\\
b,\\
{\left( { – \dfrac{1}{3}} \right)^2} – {\left( { – \dfrac{{12}}{{17}}} \right)^0} + {\left( { – \dfrac{1}{2}} \right)^3}{.4^2}\\
= \dfrac{1}{9} – 1 + \dfrac{{ – 1}}{8}.16\\
= – \dfrac{8}{9} – 2 = – \dfrac{{26}}{9}\\
2,\\
a,\\
{7^6} + {7^5} – {7^4} = {7^4}.\left( {{7^2} + 7 – 1} \right) = {7^4}.55\\
55 \vdots 11 \Rightarrow \left( {{7^4}.55} \right) \vdots 11\\
\Rightarrow \left( {{7^6} + {7^5} – {7^4}} \right) \vdots 11\\
b,\\
{10^9} + {10^8} + {10^7} = {10^7}.\left( {{{10}^2} + 10 + 1} \right) = {10^7}.111\\
= {10^6}.10.111 = {10^6}.1110\\
1110 \vdots 222 \Rightarrow \left( {{{10}^6}.1110} \right) \vdots 222\\
\Rightarrow \left( {{{10}^9} + {{10}^8} + {{10}^7}} \right) \vdots 222
\end{array}\)