\(36+64+90=\)
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a) 45 x 76 + 90 x 12
= 45 x 76 + 45 x 2 x 12
= 45 x 76 + 45 x 24
= 45 x ( 76 + 24 )
= 45 x 100
= 4500
b) 2 x 31 x 12 + 4 x 6 x 69
= 24 x 31 + 24 x 69
= 24 x ( 31 + 69 )
= 24 x 100
= 2400
c) 36 x 28 + 36 x 82 + 64 x 69 + 64 x41
= 36 x ( 28 + 82 ) + 64 x ( 69 + 41 )
= 36 x 110 + 64 x 110
= 110 x ( 36 + 64 )
= 110 x 100
= 11 000
d) 156 ( x + 61) = 82
=> x + 61 = \(\frac{82}{156}\)
=> x + 61 = \(\frac{41}{78}\)
=> x = \(\frac{41}{78}\)- 61
=> x = \(\frac{-4717}{78}\)
45 x 76 + 90 x 12 = 45 x 76 + 45 x 2 x 12
= 45 x 76 + 45 x 24
= 45 x (76 + 24)
= 45 x 100
= 4500
b) 2 x 31 x 12 + 4 x 6 x 69 = 62 x 12 + 2 x 12 x 69
= 62 x 12 + 138 x 12
= (62 + 138) x 12
= 200 x 12 = 2400
\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+....+\frac{81}{90}\)
\(=\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+...+\frac{9}{10}\)
\(=\frac{\left(1+2+3+.....+9\right)}{10}\)
\(=\frac{45}{10}=\frac{9}{2}\)
\(S=\frac{1}{10}+\frac{2^2}{20}+\frac{3^2}{30}+....+\frac{9^2}{90}=\frac{1}{10}+\frac{2}{10}+...+\frac{9}{10}=\frac{45}{10}=\frac{9}{2}\)
Rút gọn tất cả các phân số ta có:
\(\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+\frac{4}{10}+\frac{5}{10}+\frac{6}{10}+\frac{7}{10}+\frac{8}{10}+\frac{9}{10}\)
\(=\frac{1+2+3+4+5+6+7+8+9}{10}=\frac{45}{10}=\frac{9}{2}\)
\(=\dfrac{1}{15}+\dfrac{2}{15}+\dfrac{3}{15}+...+\dfrac{9}{15}\)
\(=\dfrac{1+2+3+...+9}{15}\)
\(=\dfrac{45}{15}=3\)
1/10 + 4/20 + 9/30 + 16/40 + 25/50 + 36/60 + 49/70 + 64/80 + 81/90
= 1/10 + 2/10 + 3/10 + 4/10 + 5/10 + 6/10 + 7/10 + 8/10 + 9/10
=(1+2+3+....+9) /10
=(1+9)x9:2 /10
=45/10=4,5
chắc chắn đúng đó
\(M=\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+...+\frac{81}{90}\)
\(M=\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+\frac{4}{10}+...+\frac{9}{10}\)
\(M=\frac{\left(9+1\right)\cdot\left(9-1+1\right):2}{10}\)
\(M=\frac{10\cdot9:2}{10}=4,5\)
190
ủng hộ nha
\(36+64+90=100+90=90\)
ai k mình k lại