1+2+3+4+5+6+7+8+9X2
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1+2+3+4+5+6+7+8+9x2:5 = 1+2+3+4+5+6+7+8+18:5=1+2+3+4+5+6+7+8+3.6=39.6
`3-4/5:1/3`
`=3-4/5xx3/1`
`=3-12/5`
`=15/5-12/5`
`=3/5`
`5/9xx2/7-3/7`
`=10/63-3/7`
`=10/63-27/63`
`=-17/63`
`12/8-3/4+3`
`=12/8-6/8+24/8`
`=30/8=15/4`
a) \(1678\cdot24+77\cdot1678-1678=1678\left(24+77-1\right)=167800\)
b) Ta có: \(\dfrac{2}{5}+\dfrac{4}{11}+\dfrac{3}{5}+\dfrac{18}{11}+\dfrac{1}{4}+\dfrac{1}{6}\)
\(=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{4}{11}+\dfrac{18}{11}\right)+\dfrac{1}{4}+\dfrac{1}{6}\)
\(=3+\dfrac{1}{4}+\dfrac{1}{6}\)
\(=\dfrac{36}{12}+\dfrac{3}{12}+\dfrac{2}{12}=\dfrac{41}{12}\)
\(1,\)\(\left(2x+3\right)^2=4x^2+12x+9\)
\(2,\)\(\left(3x+2y\right)^2=9x^2+12xy+4x^2\)
\(3,\)\(\left(3a-1\right)^2=9x^2-6x+1\)
\(4,\)\(\left(a-2\right)^2=a^2-4a+4\)
\(5,\)\(\left(1-5a\right)^2=1-10a+25a^2\)
\(6,\)\(\left(x-4\right)^3=x^3-12a^2+48a-64.\)
\(7,\)\(\left(x^2-2y\right)^2=x^4-4x^2y-4y^2\)
\(8,\)\(\left(5x^2-2\right)\left(5x^2+2\right)=25x^4-4\)
\(9,\)\(\left(2a^2-7\right)\left(2a^2+7\right)=4a^4-49\)
\(10,\)\(\left(x-1\right)\left(x^2+x+1\right)=x^3-1\)
\(11,\)\(\left(x^3-2\right)\left(x^6+2x^3+4\right)=x^9-8\)
\(12,\)\(\left(3x+2\right)\left(9x^2-6x+4\right)=27x^3+8\)
\(13,\)\(\left(x^2+3\right)\left(x^4-3x^2+9\right)=x^6+27\)
1, ( 2x + 3 )2 = 4x2 + 12x + 9
2, ( 3x + 2y )2 = 9x2 +12xy + 4y2
3 ( 3a - 1 )2 = 9a2 - 6x + 1
4, ( a - 2 )2 = a2 - 4a + 4
5, ( 1 - 5a )2 = 1 - 10a + 25a2
6, ( x- 4 )3 = x3 - 12x2 + 48x - 64
7, ( x2 - 2y )2 = x4 - 4x2y + 4y2
8, ( 5X2 - 2 ).( 5X2 + 2 ) = 25X2 - 4
9, ( 2a2 - 7 ).( 2a2 + 7 ) = 4a4 - 49
10, ( x - 1 ).( x2 + x + 1 ) = x3 - 1
5: \(=3-\dfrac{1}{4}+\dfrac{2}{3}-5+\dfrac{1}{3}+\dfrac{6}{5}-6+\dfrac{7}{4}-\dfrac{3}{2}\)
\(=3-5-6+\dfrac{-1}{4}+\dfrac{7}{4}+\dfrac{2}{3}+\dfrac{1}{3}+\dfrac{6}{5}-\dfrac{3}{2}\)
\(=-8+\dfrac{3}{2}+1+\dfrac{-3}{10}\)
\(=-7+\dfrac{15-3}{10}=-7+\dfrac{6}{5}=-\dfrac{29}{5}\)
6: \(=6-\dfrac{2}{3}+\dfrac{1}{2}-5-\dfrac{5}{3}+\dfrac{3}{2}-3+\dfrac{7}{3}-\dfrac{5}{2}\)
\(=6-5-3-\dfrac{2}{3}-\dfrac{5}{3}+\dfrac{7}{3}+\dfrac{1}{2}+\dfrac{3}{2}-\dfrac{5}{2}\)
\(=-2-\dfrac{1}{2}=-\dfrac{5}{2}\)
7: \(=\dfrac{5}{3}-\dfrac{3}{7}+9-2-\dfrac{5}{7}+\dfrac{2}{3}+\dfrac{8}{7}-\dfrac{4}{3}-10\)
\(=9-2-10+\dfrac{5}{3}+\dfrac{2}{3}-\dfrac{4}{3}+\dfrac{-3}{7}-\dfrac{5}{7}+\dfrac{8}{7}\)
=-3+1
=-2
8: \(=8-\dfrac{9}{4}+\dfrac{2}{7}+6+\dfrac{3}{7}-\dfrac{5}{4}-3-\dfrac{2}{4}+\dfrac{9}{7}\)
\(=8+6-3+\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{9}{7}-1-\dfrac{2}{4}\)
\(=11+2-1-\dfrac{1}{2}\)
=11+1/2
=11,5
1+2+3+4+5+6+7+8+9X2=1+2+3+4+5+6+7+8+18=54
1+2+3+4+5+6+7+8+9x2=1+2+3+4+5+6+7+8+18=54