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( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x ( 42 - 6 x 7 )
= ( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x ( 42 - 42 )
= ( 5 + 10 + 15 + 20 + 25 + 30 + 35 ) x 0
= 0
Lay (59/18 + 46/9) + (75/14 + 15/7) + (5/2 + 47/18)
De et a
2/3 * 10/21 * 3/2 = (2/3 * 3/2) * 10/21 = 1 * 10/21 = 10/21
22/5 * 12 * 5/12 = 22/5 * (12 * 5/12) = 22/5 * 5 =22
7/2 * 28/81 * 2/7= (7/2 * 2/7) * 28/81 = 1 * 28/81 =28/81
5/17 * 21/4 * 47/15 * 0 = 0
~Study well~
#Seok_Jin#
1+2+3+4+5+6+7+8+9:9
=1+2+3+4+5+6+7+8+1
=(1+1)+(2+8)+(3+7)+(4+6)+5
=2+10+10+10+5
=(2+5)+(10+10+10)
=7+30
=37
\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\)
\(=\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
\(=\frac{1}{2}+\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{5}-\frac{1}{5}\right)-\frac{1}{6}\)
\(=\frac{1}{2}-\frac{1}{6}\)
\(=\frac{1}{3}\)
\(a,\dfrac{5}{9}\times\dfrac{5}{2}+\dfrac{4}{9}\times\dfrac{5}{2}=\dfrac{5}{2}\times\left(\dfrac{5}{9}+\dfrac{4}{9}\right)=\dfrac{5}{2}\times1=\dfrac{5}{2}\)
\(12\times\dfrac{3}{4}-\dfrac{3}{4}\times\dfrac{12}{7}=\dfrac{3}{4}\times\left(12-\dfrac{12}{7}\right)=\dfrac{3}{4}\times\dfrac{72}{7}=\dfrac{54}{7}\)