Bài 1:
1.1. Tìm x
a, -x-3/4=-8/11
b, -1 và 3/5x=1 và 1/15
1.2. Tính nhanh
a, A=(7-3/4+1/3)-(-6+5/4-4/3)-(13-7/4+5/3)
b, B=5/9:(1/11-5/22)+5/9:(1/15-2/3)
Bài 1:
1.1. Tìm x
a, -x-3/4=-8/11
b, -1 và 3/5x=1 và 1/15
1.2. Tính nhanh
a, A=(7-3/4+1/3)-(-6+5/4-4/3)-(13-7/4+5/3)
b, B=5/9:(1/11-5/22)+5/9:(1/15-2/3)
Đáp án:
Giải thích các bước giải:
bài 1:
a) `-x-3/4=-8/11`
`⇔-x=-8/11+3/4`
`⇔-x=1/44`
`⇔x=-1/44`
`b) (-1(3/5))x=1(1/15)`
`⇔-8/5.x=16/15`
`⇔x=16/15.(-5/8)`
`⇔x=-2/3`
bài 2:
a) `A=(7-3/4+1/3)-(-6+5/4-4/3)-(13-7/4+5/3)`
`A=7-3/4+1/3+6-5/4+4/3-13+7/4-5/3`
`A=(7+6-13)+(1/3+4/3-5/3)+(7/4-5/4-3/4)`
`A=0+0-1/4=-1/4`
b) `B=5/9:(1/11-5/22)+5/9:(1/15-2/3)`
`B=5/9:(-3/22)+5/9:(-3/5)`
`B=5/9.(-22/3)+5/9.(-5/3)`
`B=5/9(-22/3-5/3)`
`B=5/9.(-27/3)`
`B=5/9.(-9)=-5`
Đáp án:
$1.1
a) x=\dfrac{-1}{44}\\
b)x=\dfrac{-2}{3}\\
1.2)
a)
A=\dfrac{-1}{4}\\
b)
B=-5$
Giải thích các bước giải:
$1.1
a) -x-\dfrac{3}{4}=\dfrac{-8}{11}\\
\Leftrightarrow x=\dfrac{-3}{4}+\dfrac{8}{11}\\
\Leftrightarrow x=\dfrac{-33}{44}+\dfrac{32}{44}\\
\Leftrightarrow x=\dfrac{-1}{44}\\
b) -1\dfrac{3}{5}x=1\dfrac{1}{15}\\
\Leftrightarrow \dfrac{-8}{5}x=\dfrac{16}{15}\\
\Leftrightarrow x=\dfrac{16}{15}.\dfrac{5}{-8}\\
\Leftrightarrow x=\dfrac{-2}{3}\\
1.2)
a)
A=\left ( 7-\dfrac{3}{4}+\dfrac{1}{3} \right )-\left ( -6+\dfrac{5}{4}-\dfrac{4}{3} \right )-\left ( 13-\dfrac{7}{4}+\dfrac{5}{3} \right )\\
= 7-\dfrac{3}{4}+\dfrac{1}{3} +6-\dfrac{5}{4}+\dfrac{4}{3} – 13+\dfrac{7}{4}-\dfrac{5}{3} \\
=(7+6-13)+\left ( \dfrac{-3}{4}-\dfrac{5}{4}+\dfrac{7}{4} \right )+\left ( \dfrac{1}{3}+\dfrac{4}{3}-\dfrac{5}{3} \right )\\
=\dfrac{-1}{4}+\dfrac{0}{3}\\
=\dfrac{-1}{4}\\
b)
B=\dfrac{5}{9}:\left ( \dfrac{1}{11}-\dfrac{5}{22} \right )+\dfrac{5}{9}:\left ( \dfrac{1}{15}-\dfrac{2}{3} \right )\\
=\dfrac{5}{9}:\left ( \dfrac{2}{22}-\dfrac{5}{22} \right )+\dfrac{5}{9}:\left ( \dfrac{1}{15}-\dfrac{10}{15} \right )\\
=\dfrac{5}{9}:\dfrac{-3}{22}+\dfrac{5}{9}:\dfrac{-9}{15}\\
=\dfrac{5}{9}.\dfrac{22}{-3}+\dfrac{5}{9}.\dfrac{-15}{9}\\
=\dfrac{-110}{27}+\dfrac{-25}{27}\\
=\dfrac{-135}{27}\\
=-5$