Tính bằng cách hợp lí :
S= 3/4 - 0,25 - [ 7/3 + ( -9/2 )] - 5/6
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
\(\begin{array}{l}\frac{7}{6}.3\frac{1}{4} + \frac{7}{6}.( - 0,25)\\ = \frac{7}{6}.\frac{{13}}{4} + \frac{7}{6}.\frac{{ - 25}}{{100}}\\ = \frac{7}{6}.\frac{{13}}{4} + \frac{7}{6}.\frac{{ - 1}}{4}\\ = \frac{7}{6}.[\left( {\frac{{13}}{4} + ( - \frac{1}{4})} \right)]\\ = \frac{7}{6}.\frac{{12}}{4}\\ = \frac{7}{6}.3\\ = \frac{7}{2}\end{array}\)
1/2 + 2/3 - 3/4 * 4/5 * 5/6 * 6/7 * 7/8 * 8/9 *...* 29/30 : 6/10
= 1/2 + 2/3 - 1/10 : 6/10
= 1/2 + 2/3 - 1/6
= 1
a: \(B=\frac12-\left\lbrack\frac38+\left(-\frac74\right)\right\rbrack\)
\(=\frac12-\frac38+\frac74\)
\(=\frac48-\frac38+\frac{14}{8}=\frac{15}{8}\)
b: \(-\frac{4}{12}-\left(-\frac{13}{39}-0,25\right)+0,75\)
\(=-\frac13+\frac13+0,25+0,75\)
=0,25+0,75
=1
c: \(\frac12-\frac13+\frac{1}{23}+\frac16\)
\(=\left(\frac12-\frac13+\frac16\right)+\frac{1}{23}\)
\(=\left(\frac16+\frac16\right)+\frac{1}{23}=\frac13+\frac{1}{23}=\frac{26}{69}\)
d: \(\left(-\frac{13}{7}-\frac49\right)-\left(-\frac{10}{7}-\frac49\right)\)
\(=-\frac{13}{7}-\frac49+\frac{10}{7}+\frac49\)
\(=-\frac{13}{7}+\frac{10}{7}=-\frac37\)
e: \(\left(\frac78-\frac52+\frac47\right)-\left(-\frac37+1-\frac{13}{8}\right)\)
\(=\frac78-\frac52+\frac47+\frac37-1+\frac{13}{8}\)
\(=\frac{20}{8}-\frac52=0\)
f: \(-\frac37+\left(3-\frac34\right)-\left(2,25-\frac{10}{7}\right)\)
\(=-\frac37+3-\frac34-2,25+\frac{10}{7}\)
\(=\frac77+0,75-\frac34\)
=1
g: \(\left(\frac53-\frac37+9\right)-\left(2+\frac57-\frac23\right)+\left(\frac87-\frac43-10\right)\)
\(=\frac53-\frac37+9-2-\frac57+\frac23+\frac87-\frac43-10\)
\(=\left(\frac53+\frac23-\frac43\right)+\left(-\frac37-\frac57+\frac87\right)+\left(9-2-10\right)\)
\(=\frac33+7-10=1-3=-2\)
bài 1.tính bằng cách hợp lí nhất :
a) 1/7 + 2/7 + 3/7 + ..... 3 5/7 + 3 6/7
b) 3/5x 3 5/9 + 6/5 x 11/9
\(=\left(9-8-...-2-1\right)\left(500\cdot9-500\cdot9\right)=0\)
b)
\(=\frac{3}{7}\left(\frac{9}{11}+\frac{2}{11}\right)\)
\(=\frac{3}{7}.1=\frac{3}{7}\)
\(S=\dfrac{3}{4}-\dfrac{1}{4}-\left(\dfrac{7}{3}-\dfrac{9}{2}\right)-\dfrac{5}{6}\)
\(=\left(\dfrac{3}{4}-\dfrac{1}{4}+\dfrac{18}{4}\right)-\left(\dfrac{14}{6}+\dfrac{5}{6}\right)\)
\(=\dfrac{20}{4}-\dfrac{19}{6}=\dfrac{11}{6}\)
cảm ơn nha