1.A
2.B
3.C
4.A
5.B
6.Mình kh có thấy được
7.A
8.B
9.C
10.C
1. \(60\div\left[15-\left(7-4\right)^2\right]=60\div\left[15-3^2\right]=60\div\left[15-9\right]=60\div6=10\)
\(b,113-5.\left[2^3-\left(2^3+\left(-6\right)\right)\right]=113-5.\left[2^3-\left(8+\left(-6\right)\right)\right]=113-5.\left[2^3-2\right]=113-5.\left[8-2\right]=113-5.6=113-30=83\)
\(c,\left(-27\right).1011-27.\left(-12\right)+27.\left(-1\right)=27.\left(-1011--12+-1\right)=27.-1000=-27000\)
\(d,\left|2^3+\left(1+\left(3-1\right)^2\right)\right|\div13=\left|2^3+\left(1+2^2\right)\right|\div13=\left|2^3+\left(1+4\right)\right|\div13=\left|2^3+5\right|\div13=\left|8+5\right|\div13=13\div13=1\)
2, \(a,17-3.x=2\)
\(3.x=17-2\)
\(3.x=15\)
\(x=15\div3\)
\(x=5\)
\(b,5^{x-1}=31+2.\left(-3\right)\)
\(5^{x-1}=31+-6\)
\(5^{x-1}=25\)
\(5^{x-1}=5^2\)
\(x-1=2\)
\(x=2+1\)
\(x=3\)
\(c,720\div\left[41-\left(2x-5\right)\right]=2^3.5\)
\(720\div\left[41-\left(2x-5\right)\right]=40\)
\(41-\left(2x-5\right)=720\div40\)
\(41-\left(2x-5\right)=18\)
\(2x-5=41-18\)
\(2x-5=23\)
\(2x=23+5\)
\(2x=28\)
\(x=28\div2\)
\(x=14\)
3, giải
\(8=2^3;10=2.5;12=2^2.3\)
\(BCNN\left\{8;10;12\right\}=2^3.3.5=120\)
\(BC\left\{120\right\}=\left\{240;360;480;...\right\}\)
mà số hs của trường đó trong khoảng \(300\le x\le400\)
\(\Rightarrow\) số hs của trường đó là: 360
