Toán Lớp 8: Bài 3: Tìm x:
b) x + 5×2= 0
c) 3x(x –2) –x(3x –1) = 0
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Toán Lớp 8: Bài 3: Tìm x:
b) x + 5×2= 0
c) 3x(x –2) –x(3x –1) = 0
Comments ( 2 )
Giải đáp+Lời giải và giải thích chi tiết:
Bài 3:
b) x + 5x^2 = 0
<=> x(1 + 5x) = 0
<=>\(\left[ \begin{array}{l}x=0\\1 + 5x = 0\end{array} \right.\)
<=>\(\left[ \begin{array}{l}x=0\\ 5x = -1\end{array} \right.\)
<=>\(\left[ \begin{array}{l}x=0\\ x = \dfrac{-1}{5}\end{array} \right.\)
Vậy x in {0; -1/5}
c) 3x(x-2) – x(3x-1)=0
<=> 3x^2 – 6x – 3x^2 + x = 0
<=> (3x^2 – 3x^2) – (6x – x) =0
<=> -5x = 0
<=> x =0
Vậy x = 0
b,
x + 5x^2= 0
<=>x(5x+1)=0
<=>[(x=0),(5x+1=0):}
<=>[(x=0),(x=-1/5):}
Vậy x=0;x=-1/5
c,
3x(x –2) –x(3x –1) = 0
<=>3x.x-3x.2-x.3x+x.1=0
<=>3x^2-6x-3x^2+x=0
<=>-5x=0
<=>x=0
Vậy x=0