a) (x + 3)^2 - 4x - 12 = 0
<=> (x + 3)^2 - 4(x + 3) = 0
<=> (x + 3)(x - 1) = 0
<=> x = -3 hoặc x = 1
b) x(x + 5)(x- 5) - (x - 3)(x^2 + 3x + 9) = 7
<=> x^3 - 25x - x^3 + 27 = 7
<=> -25x + 27 = 7
<=> x = 4/5
a/ \(\left(x+3\right)^2-4x-12=0\)
\(\left(x+3\right)^2-4\left(x+3\right)=0\)
\(\left(x+3\right)\left(x+3-4\right)=0\)
\(\left[{}\begin{matrix}x+3=0\Rightarrow x=-3\\x+3-4=0\Rightarrow x=1\end{matrix}\right.\)
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b/ \(x\left(x+5\right)\left(x-5\right)-\left(x-3\right)\left(x^2+3x+9\right)=7\)
\(x\left(x^2-25\right)-\left(x^3-27\right)=7\)
\(x^3-25x-x^3+27=7\)
\(-25x=-20\)
\(x=\dfrac{20}{25}=\dfrac{4}{5}\)
a, <=>x2 +6x+9-4x-12=0
<=> x2 +2x -3=0
<=> x2 +3x -x-3=0
<=> x.(x+3) - (x+3) =0
<=> (x-1)(x+3)=0
<=> x=1 hoặc x=-3
b, <=> x(x2 -25) - (x-3)(x+3)2 -7=0
<=> x3 -25x + (9-x2) (x+3) -7=0
<=> x3 -25x+ 9x+27-x3 -3x2 -7=0
<=> -3x2 -16x +20=0
<=>(3x-10)(x-2) =0 (đoạn này tự phân tích nha ^ ^)
<=> x= 10/3 hoặc x=2
Chúc bạn học tốt nha!
a, (x+3)2-4x-12=0
x+6x+9-4x-12=0
(x+6x-4x)+(9-12)=0
3x-3=0
3x=0+3
3x=3
x=3:3
x=1
Vậy x=1
b, x(x+5)(x-5)-(x-3)(x2+3x+9)=7
x(x2-52)-(x-3)(x2+3x+32)=7
x3-25x-x3+33=7
(x3-x3)-25x+27=7
-25x=7-27
-25x=-20
x=-20:(-25)
x=0,8
Vậy x=0,8
a)(x+3)2-4x-12=0
(x+3)2-4(x+3)=0
(x+3)(x-1)=0
TH1:x+3=0\(\Rightarrow\)x=-3
TH2:x-1=0\(\Rightarrow\)x=1
b)x(x+5)(x-5)-(x-3)(x2+3x+9)=7
x(x2-25)-x3+27=7
x3-25x-x3=-20
-25x=-20
x=4/5
a: \(\Leftrightarrow\left(x+3\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=1\end{matrix}\right.\)
