7+3 nhân 4 = ?
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a) 5 : 3/4 - 4 4/5 : 3/4
= 5 . 4/3 - 24/5 . 4/3
= (5 - 24/5) . 4/3
= 1/5 × 4/3
= 4/15
b) -3/5 . 2/7 + (-3/7) . 3/5 + (-3/7)
= (-3/7) . (2/5 + 3/5 + 1)
= (-3/7) . 2
= -6/7
c) [(-4 2/7) . 7/11 + 7/11 . (5 1/3)] . 5 - 5 2/3
= (-30/7 . 7/11 + 7/11 . 16/3) . 5 - 17/3
= (-30/11 + 112/33) . 5 - 17/3
= 2/3 . 5 - 17/3
= 10/3 - 17/3
= -7/3
d) 5/39 . [(7 4/5) . (1 2/3) + (8 1/3) . (7 4/5)]
= 5/39 . (39/5 . 5/3 + 25/3 . 39/5)
= 5/39 . 39/5 . (5/3 + 25/3)
= 1 . 10
= 10
=
Viết phân số thích hợp vào chỗ chấm:
A) 3/4 nhân ( 5/6+6/5 )= 3/4 nhân 5/6+3/4 nhân 6/5
B) 7/5 nhân ( 4/7-2/5 )= 7/5 nhân 4/7- 7/5 nhân 2/5
a) \(\dfrac{3}{7}\)
b)\(\dfrac{9}{4}\)
c)\(\dfrac{1}{3}\)
d)\(\dfrac{41}{32}\)
e)\(\dfrac{73}{60}\)
\(B=\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{27.30}\)
\(B=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{27}-\frac{1}{30}\)
\(B=1-\frac{1}{30}\)
\(\Rightarrow B=\frac{29}{30}\)
Cho \(A=\left(-\dfrac{4}{7}\right)^3\times\left(-\dfrac{4}{7}\right)^4\times\left(\dfrac{4}{7}\right)^5\)
\(A=\left(-\dfrac{4}{7}\right)^{3+4}\times\left(\dfrac{4}{7}\right)^5\)
\(A=\left(-\dfrac{4}{7}\right)^7\times\left(\dfrac{4}{7}\right)^5\)
\(-A=-\left[\left(-\dfrac{4}{7}\right)^7\times\left(\dfrac{4}{7}\right)^5\right]\)
\(-A=\left(-\dfrac{4}{7}\right)^7\times\left(-\dfrac{4}{7}\right)^5\)
\(-A=\left(-\dfrac{4}{7}\right)^{7+5}\)
\(-A=\left(-\dfrac{4}{7}\right)^{12}\)
\(A=-\left(\dfrac{4}{7}\right)^{12}\)
\(4^2\cdot120-4^3\cdot17+4^2\cdot34\)
\(=4^2\left(120-4\cdot17+34\right)\)
\(=16\left(120-68+34\right)\)
\(=16\cdot86=1088\)
a) \(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}\)
\(=1-\frac{1}{4}\)
\(=\frac{3}{4}\)
b) \(\frac{4}{7}\times\frac{8}{9}+\frac{4}{7}\times\frac{1}{9}\)
\(=\frac{4}{7}\times\left(\frac{8}{9}+\frac{1}{9}\right)\)
\(=\frac{4}{7}\times1\)
\(=\frac{4}{7}\)
c) \(\frac{13}{6}\times\frac{3}{8}-\frac{3}{8}\times\frac{7}{6}\)
\(=\frac{3}{8}\times\left(\frac{13}{6}-\frac{7}{6}\right)\)
\(=\frac{3}{8}\times1\)
\(=\frac{3}{8}\)
d) \(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+...+\frac{1}{9x10}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\)
\(=1-\frac{1}{10}\)
\(=\frac{9}{10}\)
7 +3 x 4
= 7 + 12
= 19
7 + 3 x 4
= 7 + 12
= 19