4x8+19-x=28
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9/5 : 7/4 + 3/4 x 8/7
= (9/5 : 8/7) x (7/4 + 3/4)
= 63/40 x 5/2
= 63/16
7 x 3/14 - 1/14
= 3/2 - 1/4
= 5/4
\(\dfrac{9}{5}:\dfrac{7}{4}+\dfrac{3}{4}\times\dfrac{8}{7}\)
\(=\dfrac{9}{5}\times\dfrac{4}{7}+\dfrac{3}{4}\times\dfrac{8}{7}\)
\(=\dfrac{36}{35}+\dfrac{6}{7}\)
\(=\dfrac{66}{35}\)
\(7\times\dfrac{3}{14}-\dfrac{1}{14}\)
\(=\dfrac{3}{2}-\dfrac{1}{14}\)
\(=\dfrac{10}{7}\)
Lời giải:
\(\frac{3}{4}\times \frac{8}{9}\times \frac{15}{16}\times ....\times \frac{99}{100}\)
\(=\frac{3\times 8\times 15\times ....\times 99}{4\times 9\times 16\times ....\times 100}\)
\(=\frac{(1\times 3)\times (2\times 4)\times (3\times 5)\times ...\times (9\times 11)}{2\times 2\times 3\times 3\times 4\times 4\times ....\times 10\times 10}\)
\(=\frac{(1\times 2\times 3\times ...\times 9)\times (3\times 4\times 5\times ....\times 11)}{(2\times 3\times 4\times....\times 10)\times (2\times 3\times 4\times ...\times 10)}\)
\(=\frac{1\times 2\times 3\times ....\times 9}{2\times 3\times 4\times ....\times 10}\times \frac{3\times 4\times 5\times ...\times 11}{2\times 3\times 4\times ...\times 10}\)
\(=\frac{1}{10}\times \frac{11}{2}=\frac{11}{20}\)
\(a.13.\left(78+22\right)=13.100=1300\)
\(b.25.70+28.25+25.2=25.\left(70+28+2\right)=25.100=2500\)
\(c.\dfrac{15.3.14.2.19}{19.14.15}=6\)
\(d.\dfrac{132.70.60}{12.35.20}=\dfrac{11.12.35.2.20.3}{12.35.20}=66\)
X + 7 = 36
X = 36 − 7
X = 29
19 + x = 58
X = 58 − 19
X = 39
X + 28 = 75
X = 75 − 28
X = 47
Ta có:
\(\dfrac{-28}{4}< x< \dfrac{19}{-6}\)
\(\Rightarrow-7< x< 3,1\)
\(\Rightarrow x=\left\{-6;-5;-4;-3;-2;-1;0;1;2;3\right\}\)
32 + 19 - x = 28
51 - x = 28
x = 51 - 28 = 23
Lời giải:
$4\times 8+19-x=28$
$32+19-x=28$
$51-x=28$
$x=51-28=23$