12,
a, $x^2=4$`<=>`\(\left[ \begin{array}{l}x=2\\x=-2\end{array} \right.\)
Vậy: ...
b, $x^2=5$`<=>`\(\left[ \begin{array}{l}x=\sqrt5\\x=-\sqrt5\end{array} \right.\)
Vậy: ...
c, $x^2=0$`<=>`$x=0$
Vậy: ...
d, $x^2=1$`<=>`\(\left[ \begin{array}{l}x=1\\x=-1\end{array} \right.\)
Vậy: ...
13,
a, $x^2-9=0$`<=>`$x^2=9$`<=>`\(\left[ \begin{array}{l}x=3\\x=-3\end{array} \right.\)
Vậy: ...
b, $x^2+1=0$`<=>`$x^2=-1$`<=>`x thuộc rỗng
Vậy: ...
c, $x^2=2$`<=>`\(\left[ \begin{array}{l}x=\sqrt2\\x=-\sqrt2\end{array} \right.\)
Vậy: ...
d, $x^2-3=0$`<=>`$x^2=3$`<=>`\(\left[ \begin{array}{l}x=\sqrt3\\x=-\sqrt3\end{array} \right.\)
Vậy: ...
14,
a, $x^2+1=82$`<=>`$x^2=81$`<=>`\(\left[ \begin{array}{l}x=9\\x=-9\end{array} \right.\)
Vậy: ...
b, $x^2+\frac{7}{4}=\frac{23}{4}$`<=>`$x^2=4$`<=>`\(\left[ \begin{array}{l}x=2\\x=-2\end{array} \right.\)
Vậy: ...
c, $2x^2=6$`<=>`$x^2=3$`<=>`\(\left[ \begin{array}{l}x=\sqrt3\\x=-\sqrt3\end{array} \right.\)
Vậy: ...
d, $7x^2=9$`<=>`$x^2=13$`<=>`\(\left[ \begin{array}{l}x=\sqrt13\\x=-\sqrt13\end{array} \right.\)
Vậy: ...
15,
a, $(x-1)^2=9$`<=>`\(\left[ \begin{array}{l}x-1=3\\x-1=-3\end{array} \right.\)`<=>`\(\left[ \begin{array}{l}x=4\\x=-2\end{array} \right.\)
Vậy: ...
b, $(2x+3)^2=25$`<=>`\(\left[ \begin{array}{l}2x+3=5\\2x+3=-5\end{array} \right.\)`<=>`\(\left[ \begin{array}{l}2x=2\\2x=-8\end{array} \right.\)`<=>`\(\left[ \begin{array}{l}x=1\\x=-4\end{array} \right.\)
Vậy: ...
