Toán Lớp 6: tìm x biết :
4.7+900:(x+3)^2=32
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Toán Lớp 6: tìm x biết :
4.7+900:(x+3)^2=32
Comments ( 2 )
4 * 7 + 900 : (x + 3)^2 = 32
28 + 900 : (x + 3)^2 = 32
900 : (x + 3)^2 = 32 – 28
900 : (x + 3)^2 = 4
(x + 3)^2 = 900 : 4
(x + 3)^2 = 225
(x + 3)^2 = 15^2 hoặc (x + 3)^2 = (-15)^2
Ta có:
TH1:
(x + 3)^2 = 15^2
x + 3 = 15
x = 12
TH2:
(x + 3)^2 = (-15)^2
x + 3 = -15
x = -18
Vậy x = 12 hoặc x = -18
Answer
4 . 7 + 900 : (x + 3)^2 = 32
=> 28 + 900 : (x + 3)^2 = 32
=> 900 : (x + 3)^2 = 32 – 28
=> 900 : (x + 3)^2 = 4
=> (x + 3)^2 = 900 : 4
=> (x + 3)^2 = 225
=> (x + 3)^2 = (+-15)^2
=> x + 3 = +-15
=> $\left[\begin{matrix} x + 3 = 15\\ x + 3 = -15\end{matrix}\right.$
=> $\left[\begin{matrix} x = 15 – 3\\ x = -15 – 3\end{matrix}\right.$
=> $\left[\begin{matrix} x = 12\\ x = -18\end{matrix}\right.$
Vậy x \in {12 ; -18}