a, \(\dfrac{38}{7}\) + ( \(\dfrac{16}{7}\) - \(\dfrac{5}{3}\))

= \(\dfrac{38}{7}\) + \(\dfrac{16}{7}\) - \(\dfrac{5}{3}\)

= \(\dfrac{54}{7}\) - \(\dfrac{5}{3}\)

= \(\dfrac{162}{21}\) - \(\dfrac{35}{21}\)

= \(\dfrac{127}{21}\)

b, \(\dfrac{29}{9}\) - ( \(\dfrac{14}{9}\) + \(\dfrac{11}{9}\) )

= \(\dfrac{29-14-11}{9}\)

= \(\dfrac{4}{9}\)

c, ( \(\dfrac{2}{7}\) + \(\dfrac{3}{8}\) + \(\dfrac{12}{7}\) + \(\dfrac{5}{8}\) ) - \(\dfrac{19}{63}\)

= ( \(\dfrac{2+12}{7}\) + \(\dfrac{3+5}{8}\)) - \(\dfrac{19}{63}\)

= \(\left(1+2\right)\) - \(\dfrac{19}{63}\)

= \(3-\dfrac{19}{63}\)

= \(\dfrac{189}{63}\) - \(\dfrac{19}{63}\)

= \(\dfrac{170}{63}\)

d, \(\dfrac{3}{7}\) . \(\dfrac{4}{9}\) + \(\dfrac{4}{9}\) . \(\dfrac{4}{7}\) - \(\dfrac{4}{9}\)

= \(\dfrac{4}{9}\) . ( \(\dfrac{3}{7}\) + \(\dfrac{3}{7}\) ) - \(\dfrac{4}{9}\)

= \(\dfrac{4}{9}\) . \(1-\dfrac{4}{9}\)

= \(\dfrac{4}{9}\) - \(\dfrac{4}{9}\)

= 0

chú ý dấu chấm là dấu nhân

1+2+3+4+5+6+7+8+9X4-2+15=85

Số cần tìm là:

1+2+3+4+5+6+7+8+9x4:2+99+1=163

Đs:163

đung 100%

Tổng Trên là : 154

1+2+3+4+5+6+7+8+9x4:2+99+1

=1+2+3+4+5+6+7+8+36:2+99+1

=1+2+3+4+5+6+7+8+18+99+1

=154

a) \(1678\cdot24+77\cdot1678-1678=1678\left(24+77-1\right)=167800\)

b) Ta có: \(\dfrac{2}{5}+\dfrac{4}{11}+\dfrac{3}{5}+\dfrac{18}{11}+\dfrac{1}{4}+\dfrac{1}{6}\)

\(=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{4}{11}+\dfrac{18}{11}\right)+\dfrac{1}{4}+\dfrac{1}{6}\)

\(=3+\dfrac{1}{4}+\dfrac{1}{6}\)

\(=\dfrac{36}{12}+\dfrac{3}{12}+\dfrac{2}{12}=\dfrac{41}{12}\)

c) \(\dfrac{7}{9\cdot7}+\dfrac{7}{9\cdot4}-\dfrac{7}{9\cdot10}\)

\(=\dfrac{7}{9}\left(\dfrac{1}{7}+\dfrac{1}{4}-\dfrac{1}{10}\right)\)

\(=\dfrac{7}{9}\cdot\left(\dfrac{20}{140}+\dfrac{35}{140}-\dfrac{14}{140}\right)\)

\(=\dfrac{7}{9}\cdot\dfrac{41}{140}=\dfrac{41}{180}\)

2) 9x²+ 12x+ 4

<=>(3x)²+ 2.3x.2+ 2² <=>(3x+ 2)²

3) 4x⁴+ 20x²+ 25

<=>(2x²)²+ 2.2x².5+ 5² <=>(2x²+5)²

4) 25x²- 20xy+ 4y²

<=> (5x)²- 2.5x.2y+ (2y)²<=> (5x-2y)²

5) 9x⁴- 12x²y+ 4y²

<=> (3x²)²- 2.3x².2.y+ (2y)²<=> (3x²- 2y)²

6) 4x⁴- 16x²y³+ 16y⁶

<=> (2x²)²- 2.2x².4y³+ (4y³)²<=> (2x²- 4y³)²

7) 9x⁴- 12x⁵+ 4x⁶

<=> (3x²)²- 2.3x².2x³+ (2x³)²<=> (3x²- 2x³)²

Đề lỗi rồi. Bạn xem lại đề.

\(\frac{4}{9}\cdot\frac{11}{15}+\frac{4}{9}\cdot\frac{4}{15}\)

\(=\frac{4}{9}\left(\frac{11}{15}+\frac{4}{15}\right)\)

\(=\frac{4}{9}\cdot1=\frac{4}{9}\)

\(\left(x-\frac{2}{3}\right).\frac{1}{6}=\frac{1}{8}\)

\(\left(x-\frac{2}{3}\right)=\frac{3}{4}\)

\(x=\frac{17}{12}\)

\(\left(x-\frac{2}{3}\right)\cdot\frac{1}{6}=18\)

\(\Rightarrow x-\frac{2}{3}=18:\frac{1}{6}=108\)

\(\Rightarrow x=108+\frac{2}{3}=\frac{326}{3}\)

\(\Rightarrow x=\frac{326}{3}\)

\(\frac{1}{3}+\frac{2}{3}\cdot x=\frac{2}{5}\)

\(\Rightarrow\frac{2}{3}\cdot x=\frac{2}{5}-\frac{1}{3}=\frac{1}{15}\)

\(\Rightarrow x=\frac{1}{15}:\frac{2}{3}=\frac{1}{10}\)

\(\Rightarrow x=0,1\)

\(\frac{5}{9}x\frac{4}{7}+\frac{5}{9}x\frac{3}{7}\)

\(=\frac{5}{9}x\left(\frac{4}{7}+\frac{3}{7}\right)\)

\(=\frac{5}{9}x1\)

\(=\frac{5}{9}\)

\(\frac{5}{9}\) x \(\frac{4}{7}\)+ \(\frac{5}{9}\)+ \(\frac{3}{7}\)

= \(\frac{5}{9}\)x ( \(\frac{4}{7}\)+ \(\frac{3}{7}\))

= \(\frac{5}{9}\) x 1 

= \(\frac{5}{9}\)

5/9*4/7+5/9*3/7

=20/63+5/21

=5/9.

a: =2/3(4/9+5/9)=2/3

d: =15/16(9/5-4/5)=15/16

e: =13/25(5-3-1)=13/25