Tìm x € Z sao cho
a) (X+1)×(3-X)=0
b) (X-2)×(2×X-1)=0
c)(3×X+9)×(1-3×X)=0
d)(X²+1)×(81-X²)=0
Thank các bạn nhìu!
Tìm x € Z sao cho
a) (X+1)×(3-X)=0
b) (X-2)×(2×X-1)=0
c)(3×X+9)×(1-3×X)=0
d)(X²+1)×(81-X²)=0
Thank các bạn nhìu!
Đáp án:
Giải thích các bước giải:
a) TH1:x+1=0 TH2:3-X=0
X=0-1 X=3-0
X=-1 X=3
vậy x={-1;3}
b) TH1 : x-2=0 th2:2x-1=0
x=2 2x=1
x=1/2
vậy x={2;1/2}
c) th1: 3X+9=0 TH2:1-3X=0
3X=-9 3X=1
X=-3 X=1/3
vậy x={-3;1/3}
d) TH1: X^2+1=0 TH2:81-X^2=0
X^2=-1(loại vì x^2 luôn lớn hơn hoặc =0) x^2=81
x=9
vậy x={9}
a) (X+1)×(3-X)=0
(=)\(\left[ \begin{array}{l}x+1=0\\3-x=0\end{array} \right.\)(=)\(\left[ \begin{array}{l}x=-1\\x=3\end{array} \right.\)
b) (X-2)×(2×X-1)=0
(=)\(\left[ \begin{array}{l}x-2=0\\2x-1=0\end{array} \right.\) (=)\(\left[ \begin{array}{l}x=2\\2x=1\end{array} \right.\) (=)\(\left[ \begin{array}{l}x=2\\x=\frac{1}{2}\end{array} \right.\)
c)(3×X+9)×(1-3×X)=0
(=)\(\left[ \begin{array}{l}3x+9=0\\1-3x=0\end{array} \right.\) (=)\(\left[ \begin{array}{l}3x=-9\\-3x=-1\end{array} \right.\) (=) \(\left[ \begin{array}{l}x=-3\\x=\frac{1}{3} \end{array} \right.\)
d)(X²+1)×(81-X²)=0
(=)\(\left[ \begin{array}{l}x^{2}+1=0 \\81-x^{2}=0 \end{array} \right.\) (=)\(\left[ \begin{array}{l}x^{2}=-1=)vô lý\\x^{2}=81\end{array} \right.\) =)x=±9