Tìm x ∈ Z d) 13-7.(3x+1) ² = -162 e) -31- 324:(x+1) ³ = -19 22/08/2021 Bởi Raelynn Tìm x ∈ Z d) 13-7.(3x+1) ² = -162 e) -31- 324:(x+1) ³ = -19
Đáp án d, 13-7.(3x + 1)² = -162 ⇔ 7.(3x + 1)² = 13 – (-162) ⇔ 7.(3x + 1)² = 175 ⇔ (3x + 1)² = 175 : 7 ⇔ (3x + 1)² = 25 ⇔ \(\left[ \begin{array}{l}(3x+1)^{2}=5^{2} \\(3x+1)^{2}=(-5)^{2}\end{array} \right.\) ⇔ \(\left[ \begin{array}{l}x=\frac{4}{3}\\x=-2\end{array} \right.\) e , -31 – 324 : (x + 1)³ = -19 ⇔ -324 : ( x+1)³ = -19 + 31 ⇔ -324 : (x +1)³ = 12 ⇔ (x + 1)³ = -27 ⇔ (x+1)³ =(-3)³ ⇔ x + 1 = -3 ⇔ x =-4 Bình luận
$d)13-7(3x+1)^2=-162 \\⇔13-7(9x^2+6x+1)=-162 \\⇔13-63x^2-42x-7=-162 \\⇔-63x^2-42x+6+162=0 \\⇔-63x^2-42x+168=0 \\⇔-21(3x-4)(x+2)=0$ ⇔\(\left[ \begin{array}{l}3x-4=0\\x+2=0\end{array} \right.\) ⇔\(\left[ \begin{array}{l}x=\dfrac{4}{3}\\x=-2\end{array} \right.\) $e)-31-324:(x+1)^3=-19 \\⇔-324:(x+1)^3=-19+31 \\⇔-324:(x+1)^3=12 \\⇔(x+1)^3=-27 \\⇔(x+1)^3=(-3)^3 \\⇔x+1=-3 \\⇔x=-4 \\Vậy\ x=-4$ Bình luận
Đáp án
d, 13-7.(3x + 1)² = -162
⇔ 7.(3x + 1)² = 13 – (-162)
⇔ 7.(3x + 1)² = 175
⇔ (3x + 1)² = 175 : 7
⇔ (3x + 1)² = 25
⇔ \(\left[ \begin{array}{l}(3x+1)^{2}=5^{2} \\(3x+1)^{2}=(-5)^{2}\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=\frac{4}{3}\\x=-2\end{array} \right.\)
e , -31 – 324 : (x + 1)³ = -19
⇔ -324 : ( x+1)³ = -19 + 31
⇔ -324 : (x +1)³ = 12
⇔ (x + 1)³ = -27
⇔ (x+1)³ =(-3)³
⇔ x + 1 = -3
⇔ x =-4
$d)13-7(3x+1)^2=-162 \\⇔13-7(9x^2+6x+1)=-162 \\⇔13-63x^2-42x-7=-162 \\⇔-63x^2-42x+6+162=0 \\⇔-63x^2-42x+168=0 \\⇔-21(3x-4)(x+2)=0$
⇔\(\left[ \begin{array}{l}3x-4=0\\x+2=0\end{array} \right.\) ⇔\(\left[ \begin{array}{l}x=\dfrac{4}{3}\\x=-2\end{array} \right.\)
$e)-31-324:(x+1)^3=-19 \\⇔-324:(x+1)^3=-19+31 \\⇔-324:(x+1)^3=12 \\⇔(x+1)^3=-27 \\⇔(x+1)^3=(-3)^3 \\⇔x+1=-3 \\⇔x=-4 \\Vậy\ x=-4$