Dấu của tam thức bậc hai !!

A.\(\left\{ {\begin{array}{*{20}{c}}{a >0}\\{\Delta \le 0}\end{array}} \right.\)

B. \(\left\{ {\begin{array}{*{20}{c}}{a >0}\\{\Delta \ge 0}\end{array}} \right.\)

C. \(\left\{ {\begin{array}{*{20}{c}}{a >0}\\{\Delta < 0}\end{array}} \right.\)

D. \(\left\{ {\begin{array}{*{20}{c}}{a < 0}\\{\Delta >0}\end{array}} \right.\)

A.\(\left\{ {\begin{array}{*{20}{c}}{a < 0}\\{\Delta \le 0}\end{array}} \right.\)

B. \(\left\{ {\begin{array}{*{20}{c}}{a < 0}\\{\Delta \ge 0}\end{array}} \right.\)

C. \(\left\{ {\begin{array}{*{20}{c}}{a >0}\\{\Delta < 0}\end{array}} \right.\)

D. \(\left\{ {\begin{array}{*{20}{c}}{a < 0}\\{\Delta >0}\end{array}} \right.\)</>

A.\[f\left( x \right) >0\,,\forall x \in \mathbb{R}\]

B. \[f\left( x \right) < 0\,,\forall x \in \mathbb{R}\]

C. f(x) không đổi dấu

D. Tồn tại x để f(x) = 0

A.\[x \in \left( {0; + \infty } \right).\]

B. \[x \in \left( { - 2; + \infty } \right).\]

C. \[\forall x \in \mathbb{R}.\]

D. \[x \in \left( { - \infty ;2} \right).\]Trả lời:

A.0

B.1

C.2

D.3

A.Dương với mọi \[x \in \mathbb{R}\].

B.Âm với mọi \[x \in \mathbb{R}\].

C.Âm với mọi \[x \in \left( { - 2 - \sqrt 3 ;1 + 2\sqrt 3 } \right)\]

D.Âm với mọi \[x \in \left( { - \infty ;1} \right)\]

A.

B.

C.

D.

A.\[b \in \left[ { - 2\sqrt 3 ;2\sqrt 3 } \right]\]

B. \[b \in \left( { - 2\sqrt 3 ;2\sqrt 3 } \right)\]

C. \[b \in \left( { - \infty ; - 2\sqrt 3 } \right] \cup \left[ {2\sqrt 3 ; + \infty } \right)\]

D. $b\in \left(-\infty ;-2\sqrt{3}\right)\cup \left(2\sqrt{3};+\infty \right)$

A.\[m \in \left( { - \infty ; - \frac{3}{5}} \right) \cup \left( {1; + \infty } \right) \setminus \left\{ 3 \right\}\]

B. \[m \in \left( { - \frac{3}{5};1} \right)\]

C. \[m \in \left( { - \frac{3}{5}; + \infty } \right)\]

D. \[m \in \mathbb{R} \setminus \left\{ 3 \right\}\]

A.\[m \le 0\;\] hoặc \[m \ge 28\].

B. m < 0 hoặc m >28.

C.0< m < 28 .

D.m >0.

A.\[{\rm{D}} = \left[ { - 4; - 1} \right) \cup \left( { - \frac{1}{2}; + \infty } \right).\]

B. \[{\rm{D}} = \left( { - \infty ; - 4} \right] \cup \left( { - 1; - \frac{1}{2}} \right).\]

C. \[{\rm{D}} = \left( { - \infty ; - 4} \right] \cup \left( { - \frac{1}{2}; + \infty } \right).\]

D. \[{\rm{D}} = \left[ { - 4; - \frac{1}{2}} \right).\]

A.\[\left( { - \infty ;1} \right) \cup \left( {3; + \infty } \right)\]

B. \[\left( { - \infty ;1} \right) \cup \left( {4; + \infty } \right)\]

C. \[\left( { - \infty ;2} \right) \cup \left( {3; + \infty } \right)\]

D. \[\left( {1;4} \right)\]

A.m < −1.

B.m >−1.

C.\[m < - \frac{4}{3}\]

D. \[m >\frac{4}{3}\]

A.a = 0.

B.a < 0

C.\[0 < a \le \frac{1}{2}\]

D. \[a \ge \frac{1}{2}\]

A.m<1.

B.m>1.

C.\[m < \frac{1}{4}\]

D. \[m >\frac{1}{4}\]

A.\[m >- \frac{1}{5}.\]

B. \[m >\frac{1}{4}.\]

C. \[m >- \frac{1}{{11}}.\]

D. \[m >\frac{1}{{32}}.\]

A.0.

B.1.

C.2.

D.3.

A.0 < m < 3

B.m < 0

C.m < 0 hoặc m >3

D.m >3