Toán Lớp 8: 1.phân tích đa thức thành nhân tử:
a.3a – 6b
b. a^2 – 4b^2
c. 3x^2 – 7x + 2
bài 2:
a.x^2 + 4x^2=0
b. 3 ( x – 201) = x – 201
c. ( x – 2 )^2 – ( 3 + 2x ) ^2 =0
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Toán Lớp 8: 1.phân tích đa thức thành nhân tử:
a.3a – 6b
b. a^2 – 4b^2
c. 3x^2 – 7x + 2
bài 2:
a.x^2 + 4x^2=0
b. 3 ( x – 201) = x – 201
c. ( x – 2 )^2 – ( 3 + 2x ) ^2 =0
Comments ( 1 )
1)a)\\
3a – 6b = 3.\left( {a – 2b} \right)\\
b){a^2} – 4{b^2} = {a^2} – {\left( {2b} \right)^2} = \left( {a – 2b} \right)\left( {a + 2b} \right)\\
c)3{x^2} – 7x + 2\\
= 3{x^2} – 6x – x + 2\\
= 3x\left( {x – 2} \right) – \left( {x – 2} \right)\\
= \left( {x – 2} \right)\left( {3x – 1} \right)\\
B2)\\
a){x^2} + 4{x^2} = 0\\
\Leftrightarrow 5{x^2} = 0\\
\Leftrightarrow {x^2} = 0\\
\Leftrightarrow x = 0\\
Vậy\,x = 0\\
b)3\left( {x – 201} \right) = x – 201\\
\Leftrightarrow 3\left( {x – 201} \right) – \left( {x – 201} \right) = 0\\
\Leftrightarrow 2\left( {x – 201} \right) = 0\\
\Leftrightarrow \left( {x – 201} \right) = 0\\
\Leftrightarrow x = 201\\
Vậy\,x = 201\\
c){\left( {x – 2} \right)^2} – {\left( {3 + 2x} \right)^2} = 0\\
\Leftrightarrow \left( {x – 2 + 3 + 2x} \right)\left( {x – 2 – 3 – 2x} \right) = 0\\
\Leftrightarrow \left( {3x + 1} \right)\left( { – x – 5} \right) = 0\\
\Leftrightarrow \left[ \begin{array}{l}
3x = – 1\\
– x = 5
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = – \dfrac{1}{3}\\
x = – 5
\end{array} \right.\\
Vậy\,x = – \dfrac{1}{3};x = – 5
\end{array}$