Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a) \(\dfrac{3}{4}=\dfrac{3x4}{4x4}=\dfrac{12}{16},\dfrac{6}{7}=\dfrac{6x2}{7x2}=\dfrac{12}{14}\)
Do 16 > 14 => \(\dfrac{12}{16}< \dfrac{12}{14}hay\dfrac{3}{4}< \dfrac{6}{7}\)
1: Rút gọn
a) \(-\dfrac{33}{51}=\dfrac{-33:3}{51:3}=\dfrac{-11}{17}\)
b) \(\dfrac{156}{-168}=\dfrac{-156}{168}=\dfrac{-156:12}{168:12}=\dfrac{-13}{14}\)
c) \(\dfrac{-75}{-100}=\dfrac{75}{100}=\dfrac{75:25}{100:25}=\dfrac{3}{4}\)
2: Quy đồng mẫu:
a) \(-\dfrac{3}{8}\) và \(\dfrac{5}{4}\)
MSC: 8
\(-\dfrac{3}{8}=\dfrac{-3}{8}\)
\(\dfrac{5}{4}=\dfrac{5\cdot2}{4\cdot2}=\dfrac{10}{8}\)
b) \(\dfrac{-7}{6}\) ; \(\dfrac{5}{12}\) và \(-\dfrac{5}{6}\)
MSC: 12
\(-\dfrac{7}{6}=\dfrac{-7\cdot2}{6\cdot2}=\dfrac{-14}{12}\)
\(\dfrac{5}{12}=\dfrac{5}{12}\)
\(\dfrac{-5}{6}=\dfrac{-5\cdot2}{6\cdot2}=\dfrac{-10}{12}\)
hộ C1: Tìm x biết
a 2x-35=15
=>2x=15+35=50
=>x=25
b 3x+17=2
=>3x=2-17=-15
=>x=5
c x+3/15=1/3
x=1/3-3/15=2/15
d x-12/4=1/2
x=1/2+12/4=7/2
a. 2x-35=15
2x=15+35
2x=50
x=50:2
x=25
Vậy x=25
b. 3x+17=2
3x=2-17
3x=-15
x=-15:3
x=-5
Vậy x=-5
c. \(\frac{x+3}{15}=\frac{1}{3}\)
\(\Rightarrow3x+9=15\)
\(3x=15-9\)
\(3x=6\)
\(x=6:3\)
\(x=3\)
Vậy x=3
d. \(\frac{x-12}{4}=\frac{1}{2}\)
\(\Rightarrow2x-24=4\)
\(2x=4+24\)
\(2x=28\)
\(x=28:2\)
\(x=14\)
Vậy x=14
Bài 1:
a) \(\dfrac{-5}{6}\ne\dfrac{10}{-14}\left(\dfrac{10}{-14}=-\dfrac{5}{7}\right).\)
b) \(\dfrac{-15}{-60}\ne\dfrac{-3}{12}\left(\dfrac{-15}{-60}=\dfrac{1}{4}\right).\)
Bài 2:
a) \(\dfrac{20}{-140}=-\dfrac{1}{7}.\)
b) \(\dfrac{4.18}{9.12}=\dfrac{72}{108}=\dfrac{2}{3}.\)
c) \(\dfrac{17.25-17.3}{2.\left(-15\right)}=\dfrac{17.\left(25-3\right)}{-30}=-\dfrac{17.22}{30}=\dfrac{374}{30}=\dfrac{187}{15}.\)
Bài 3:
a) \(\dfrac{-3}{5}< \dfrac{4}{-7}.\)
b) \(\dfrac{-4}{21}>\dfrac{-7}{35}.\)
c) \(\dfrac{-7}{24}>\dfrac{-2}{3}.\)
d) \(\dfrac{-52}{167}< \dfrac{-3}{-4}.\)
1. Rút gọn phân số
a) \(\dfrac{-12}{21}\) = \(\dfrac{-12:3}{21:3}\) = \(\dfrac{-4}{7}\)
b) \(\dfrac{-63}{81}\) = \(\dfrac{-63:9}{81:9}\) = \(\dfrac{-7}{9}\)
2. Quy đồng mẫu số
\(\dfrac{-6}{5}\) \(\dfrac{8}{-4}\)
⇒ \(\dfrac{-6}{5}\) = \(\dfrac{-8}{4}\) MSC: 20
\(\dfrac{-6}{5}\) = \(\dfrac{-24}{20}\)
\(\dfrac{-8}{4}\) = \(\dfrac{-40}{20}\)
3. So sánh phân số
\(\dfrac{6}{7}\) và \(\dfrac{11}{10}\) MSC: 70
\(\dfrac{6}{7}\) = \(\dfrac{60}{70}\)
\(\dfrac{11}{10}\) = \(\dfrac{77}{70}\)
Vì \(\dfrac{60}{70}\) < \(\dfrac{77}{70}\) nên \(\dfrac{6}{7}\) < \(\dfrac{11}{10}\)
4. Cộng hai phân số
a) \(\dfrac{3}{4}\) + \(\dfrac{-7}{6}\) MSC: 12
\(\dfrac{3}{4}\) = \(\dfrac{9}{12}\)
\(\dfrac{-7}{6}\) = \(\dfrac{-14}{12}\)
\(\dfrac{9+\left(-4\right)}{12}\) = \(\dfrac{-5}{12}\)
kcj
thấy câu hỏi dễ thì trả lời