tìm x biêt :
( 8x + 89 ) - 5x = 112 + 132
gấp :( hứa sẽ tick
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13 tháng 10 2017
1. 179 - ( 55 + 2x ) = 64
( 55 +2x) = 179 - 64
55 + 2x = 115
2x = 115 - 55
2x = 60
x = 30
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VT
8 tháng 8 2018
1)x2-3x+2
=x2-x-2x+2
=x(x-1)-2(x-1)
=(x-1)(x-2)
2)2x2+5x-7
=2x2-2x+7x-7
=2x(x-1)+7(x-1)
=(x-1)(2x+7)
3)x2+7x-8
=x2-x+8x-8
=x(x-1)+8(x-1)
=(x-1)(x+8)
4)x2+8x+7
=x2+x+7x+7
=x(x+1)+7(x+1)
=(x+1)(x+7)
5)2x2-5x-7
=2x2+2x-7x-7
=2x(x+1)-7(x+1)
=(x+1)(2x-7)
xong rồi !!
8 tháng 8 2018
Phân tích đa thức thành nhân tử:
1. x2 - 5x - 6
\(=x^2-6x+x-6\)
\(=\left(x^2-6x\right)+\left(x-6\right)\)
\(=x\left(x-6\right)+\left(x-6\right)\)
\(=\left(x+1\right)\left(x-6\right)\)
3. 1 + 3x + 2x2
\(=1+2x+x+2x^2\)
\(=\left(1+2x\right)+\left(x+2x^2\right)\)
\(=\left(1+2x\right)+x\left(1+2x\right)\)
\(=\left(1+2x\right)+\left(x+1\right)\)
4. 6 - 2x - 8x2
\(=6-8x+6x-8x^2\)
\(=\left(6+6x\right)-\left(8x+8x^2\right)\)
\(=6\left(1+x\right)-8x\left(1+x\right)\)
\(=\left(6-8x\right)\left(1+x\right)\)
5. 7 - 4x - 3x2
\(=7-7x+3x-3x^2\)
\(=\left(7-7x\right)+\left(3x-3x^2\right)\)
\(=7\left(1-x\right)+3x\left(1-x\right)\)
\(=\left(7+3x\right)\left(1-x\right)\)
8 tháng 8 2018
1) \(x^2-5x-6\\ =x^2+x-6x-6\\ =x\left(x+1\right)-6\left(x+1\right)\\ =\left(x-6\right)\left(x+1\right)\)
3) \(1+3x+2x^2\\ =2x^2+2x+x+1\\ =2x\left(x+1\right)+\left(x+1\right)\\ =\left(x+1\right)\left(2x+1\right)\)
8 tháng 8 2018
1) \(x^2-8x+7=0\)
\(\Leftrightarrow x^2-7x-x+7=0\)
\(\Leftrightarrow\left(x^2-7x\right)-\left(x-7\right)=0\)
\(\Leftrightarrow x\left(x-7\right)-\left(x-7\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-7\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x-7=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=7\end{matrix}\right.\)
2) \(5x^2-11x+6=0\)
\(\Leftrightarrow5x^2-5x-6x+6=0\)
\(\Leftrightarrow\left(5x^2-5x\right)-\left(6x-6\right)=0\)
\(\Leftrightarrow5x\left(x-1\right)-6\left(x-1\right)=0\)
\(\Leftrightarrow\left(5x-6\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}5x-6=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{6}{5}\\x=1\end{matrix}\right.\)
3) \(2x^2-3x+1=0\)
\(\Leftrightarrow2x^2-2x-x+1=0\)
\(\Leftrightarrow\left(2x^2-2x\right)-\left(x-1\right)=0\)
\(\Leftrightarrow2x\left(x-1\right)-\left(x-1\right)=0\)
\(\Leftrightarrow\left(2x-1\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-1=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=1\end{matrix}\right.\)
4) \(x^2+7x-8=0\)
\(\Leftrightarrow x^2+8x-x-8=0\)
\(\Leftrightarrow\left(x^2+8x\right)-\left(x+8\right)=0\)
\(\Leftrightarrow x\left(x+8\right)-\left(x+8\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x+8\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x+8=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-8\end{matrix}\right.\)
5) \(3x^2+7x-10=0\)
\(\Leftrightarrow3x^2-3x+10x-10=0\)
\(\Leftrightarrow\left(3x^2-3x\right)+\left(10x-10\right)=0\)
\(\Leftrightarrow3x\left(x-1\right)+10\left(x-1\right)=0\)
\(\Leftrightarrow\left(3x+10\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}3x+10=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{10}{3}\\x=1\end{matrix}\right.\)
LK
8 tháng 8 2018
1. x2 + x - 12 = x2 + 4x - 3x - 12
= x(x + 4) - 3(x + 4)
= (x - 3)(x + 4)
2. x2 - x - 12 = x2 - 4x + 3x - 12
= x(x - 4) + 3(x - 4)
= (x + 3)(x - 4)
3. x2 + 4x - 12 = x2 + 6x - 2x - 12
= x(x + 6) - 2(x + 6)
= (x - 2)(x + 6)
4. x2 + 8x + 15 = x2 + 3x + 5x + 15
= x(x + 3) + 5(x + 3)
= (x + 5)(x + 3)
5. 5x2 - 4x - 1 = 5x2 - 5x + x - 1
= 5x(x - 1) + (x - 1)
= (5x + 1)(x - 1)
( 8x + 89 ) - 5x = 112 + 132
8x + 89 - 5x = 121 + 169
( 8x - 5x ) + 89 = 290
3x + 89 = 290
3x = 290 - 89
3x = 201
x = 201 : 3
x = 67
Vậy x = 67
tks :D