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a) x-12=-9+15
x-12=24
x=24+12
x=36
Vậy x=36
b)4x -12=400
4x=412
x=412:4
x=103
Vậy x=103
c)2x -35=15
2x=50
x=50:2
x=15
Vậy x=15
d)3x+17=2
3x=-15
x=(-15):3
x=-5
Vậy x=-5
e)\(\frac{-5}{8}=\frac{x}{16}\)
\(\Rightarrow\left(-5\right).16=8.x\)
\(\Rightarrow8x=-80\)
\(\Rightarrow x=-10\)
f)\(\frac{y}{10}=-\frac{4}{8}\)
\(\Rightarrow8y=\left(-4\right).10\)
\(\Rightarrow8y=-40\)
\(\Rightarrow y=-5\)
a) x - 12 = -9 + 15
=> x - 12 = 6
=> x = 6 + 12 = 18
b) 4x - 12 = 400
=> 4x = 400 + 12 = 412
=> x = 412 : 4 = 103
c) 2x - 35 = 15
=> 2x = 15 + 35 = 50
=> x = 50 : 2 = 25
d) 3x + 17 = 2
=> 3x = 2 - 17
=> 3x = -15
=> x = -15 : 3 = -5
e) \(\frac{-5}{8}=\frac{x}{16}\)
\(=>\frac{-10}{16}=\frac{x}{16}\)
=> x = -10
f) \(\frac{y}{10}=\frac{-4}{8}\)
\(=>\frac{y}{10}=\frac{-1}{2}\)
\(=>\frac{y}{10}=\frac{-5}{10}\)
=> y = -5
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\(\left(4x+1\right)\left(x-3\right)-\left(x-7\right)\left(4x-1\right)=15\\ \Leftrightarrow4x^2+x-12x-3-\left(4x^2-28x-x+7\right)-15=0\\ \Leftrightarrow4x^2-11x-3-4x^2+29x-7-15=0\\ \Leftrightarrow18x=25\\ \Leftrightarrow x=\dfrac{25}{18}\)
Vậy \(x=\dfrac{25}{18}\)
Lời giải:
$(4x+1)(x-3)-(x-7)(4x-1)=15$
$\Leftrightarrow (4x^2-11x-3)-(4x^2-29x+7)=15$
$\Leftrightarrow 18x-10=15$
$\Leftrightarrow 18x=25$
$\Leftrightarrow x=\frac{25}{18}$
\(0,25\cdot\dfrac{7}{15}-\dfrac{1}{4}\cdot\left(-\dfrac{8}{15}\right)+2,75\)
\(=\dfrac{1}{4}\cdot\left(\dfrac{7}{15}+\dfrac{8}{15}\right)+2,75\)
\(=\dfrac{1}{4}\cdot1+2,75\)
\(=0,25+2,75\\ =3\)