-7 + x = 52
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c) \(\left|x\right|=3,5\Rightarrow\left[{}\begin{matrix}x=3,5\\x=-3,5\end{matrix}\right.\)
d) \(\left|x\right|=-2,7\Rightarrow x\in\varnothing\)
l) \(\left|x+\dfrac{3}{4}\right|-5=-2\Rightarrow\left|x+\dfrac{3}{4}\right|=3\)
\(\Rightarrow\left[{}\begin{matrix}x+\dfrac{3}{4}=3\\x+\dfrac{3}{4}=-3\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=3-\dfrac{3}{4}\\x=-3-\dfrac{3}{4}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{9}{4}\\x=\dfrac{15}{4}\end{matrix}\right.\)
Đính chính câu l \(x=-\dfrac{15}{4}\) không phải \(x=\dfrac{15}{4}\)
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a) \(19\times\left(52+38\right)-9\times\left(52+38\right)=\)
\(=\) \(19\times90-9\times90\)
\(=90\times\left(19-9\right)\)
\(=90\times10\)
\(=900\)
b) \(\dfrac{2}{5}\div\dfrac{3}{7}\times\dfrac{3}{7}\div\dfrac{2}{5}+2019=\)
\(=\left(\dfrac{2}{5}\div\dfrac{2}{5}\right)\times\left(\dfrac{3}{7}\div\dfrac{3}{7}\right)+2019\)
\(=1\times1+2019\)
\(=2019\)
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tinh nhanh :
52 x 64 + 520 x 7 - 52 x 34 = 52 x 64 + 52 x 10 x 7 - 52 x 34
=52 x ( 64 + 70 - 34 ) = 5200
52 x 64 + 520 x 7 - 52 x 34
= 52 x 64 + 52 x 10 x 7 - 52 x 34
=. 52 x 64 + 52 x 70 - 52 x 34
=52 x( 64 + 70 - 34 )
=52 x 100 = 5200
k nha
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= 23 x 0.07 + 0.07 x 52 + 0.07 x 25
= ( 23 + 52 + 25 ) x 0.07
= ( 75 + 25 ) x 0.07
= 100 x 0.07
= 7
23 x 0,07 + 7% x 52 + 7/100 x 25
= 23 x 0,07 + 0,07 x 52 + 0,07 x 25
= 0,07 x (23 + 52 + 25)
= 0,07 x 100
= 7
Chúc bạn học tốt.
😁😁😁
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Ta có: x + 5 2 + x - 2 2 + (x +7)(x -7) = 12x -23
⇔ x 2 + 10x + 25 + x 2 - 4x +4 + x 2 -49 = 12x -23
⇔ x 2 +10x+25 + x 2 -4x +4 + x 2 -49 -12x +23 =0
⇔ 3 x 2 -6x + 3 =0
⇔ x 2 -2x +1 =0
∆ ’ = - 1 2 -1.1 = 1-1 =0
Vậy phương trình đã cho có nghiệm kép: x 1 = x 2 =1
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\(-6\left(x+7\right)+\left(x-5\right)=-52\)
\(\Leftrightarrow-6x-42+x-5+52=0\)
\(\Leftrightarrow-5x+5=0\)
\(\Leftrightarrow-5x=-5\)
\(\Rightarrow x=1\)
-6.(x+7) + (x - 5) = -52
-6x + -42 + x - 5 = -52
-6x + x - 5 = -52 + 42
-6x + x - 5 = -10
-5x - 5 = - 10
-5x = -10 + 5
-5x = -5
-1x = -1
=> x = 1
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A. 64 : 16 = 4
B. 210 : 30 = 7
C. 504 : 56 = 9
D. 115 : 23 = 5