Toán

a) \(x^2=15\Leftrightarrow x=\pm\sqrt{15}\)

Vậy x = \(\pm\sqrt{15}\)

b) \(x^2=121\Leftrightarrow x=\pm\sqrt{121}=\pm11\)

Vậy x = \(\pm11\)

c) \(\left(x-2\right)^2=9\Leftrightarrow x-2=\pm\sqrt{9}=\pm3\Leftrightarrow\left[{}\begin{matrix}x-2=3\Leftrightarrow x=5\\x-2=-3\Leftrightarrow x=-1\end{matrix}\right.\)

Vậy x ∈ {-1; 5}

d) \(\left(x+6\right)^2=225\Leftrightarrow x+6=\pm\sqrt{225}=\pm15\Leftrightarrow\left[{}\begin{matrix}x+6=15\Leftrightarrow x=9\\x+6=-15\Leftrightarrow x=-21\end{matrix}\right.\)

Vậy x ∈ {-21; 9}

a/ \(x^2=15\Leftrightarrow x=\pm\sqrt{15}\)

b/ \(x^2=121\Leftrightarrow x=\sqrt{121}\Leftrightarrow x=\pm11\)

c/ \(\left(x-2\right)^2=9\Leftrightarrow\left(x-2\right)^2=3^2\Leftrightarrow\left[{}\begin{matrix}x-2=-3\\x-2=3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=5\end{matrix}\right.\)

d/ \(\left(x+6\right)^2=225\Leftrightarrow\left(x+6\right)^2=15^2\Leftrightarrow\left[{}\begin{matrix}x+6=-15\\x+6=15\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-21\\x=9\end{matrix}\right.\)

\(a,x^2=15\\ \Leftrightarrow\left[{}\begin{matrix}x=\sqrt{15}\\x=-\sqrt{15}\end{matrix}\right.\)

Vậy \(S=\left\{\sqrt{15};-\sqrt{15}\right\}\)

\(b,x^2=121\\ \Leftrightarrow x^2=11^2\\ \Leftrightarrow\left[{}\begin{matrix}x=11\\x=-11\end{matrix}\right.\)

Vậy \(S=\left\{11;-11\right\}\)

\(c,\left(x-2\right)^2=9\\ \Leftrightarrow\left(x-2\right)^2=3^2\\ \Leftrightarrow x-2=\pm3^2\\ \Leftrightarrow\left[{}\begin{matrix}x-2=3\\x-2=-3\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=5\\x=-1\end{matrix}\right.\)

Vậy \(S=\left\{-1;5\right\}\)

\(d,\left(x+6\right)^2=225\\ \Leftrightarrow\left(x+6\right)^2=15^2\\ \Leftrightarrow x+6=\pm15\\ \Leftrightarrow\left[{}\begin{matrix}x+6=15\\x+6=-15\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=9\\x=-21\end{matrix}\right.\)

Vậy \(S=\left\{9;-21\right\}\)

$\sin \alpha =2$?? $\sin \alpha \in [-1;1]$ với mọi $\alpha$ mà bạn. Bạn xem lại đề.

1: =>x^2(x^2+3)+4=0

=>x^2(x^2+3)=-4(vô lý)

2: =>(x^2+1)(x^2+3)=0

=>x^2+1=0(loại) hoặc x^2+3=0(loại)

3: =>x^2(5x^2+3)+2=0

=>x^2(5x^2+3)=-2(loại)

4: =>(x^2+2)(x^2+3)=0

=>x^2=-2(loại) hoặc x^2=-3(loại)

5: =>x^2(2x^2+3)+2=0

=>x^2(2x^2+3)=-2(loại)

a) \(\sqrt{x}=9\) (ĐK: \(x\ge0\))

\(\Leftrightarrow x=9^2\)

\(\Leftrightarrow x=81\left(tm\right)\)

b) \(\sqrt{x-2}=11\) (ĐK: \(x\ge2\))

\(\Leftrightarrow x-2=11^2\)

\(\Leftrightarrow x-2=121\)

\(\Leftrightarrow x=121+2=123\left(tm\right)\)

c) \(3\sqrt{x}-18=3\) (ĐK: \(x\ge0\))

\(\Leftrightarrow3\sqrt{x}=3+18\)

\(\Leftrightarrow3\sqrt{x}=21\)

\(\Leftrightarrow\sqrt{x}=\dfrac{21}{3}\)

\(\Leftrightarrow\sqrt{x}=7\)

\(\Leftrightarrow x=7^2\)

\(\Leftrightarrow x=49\left(tm\right)\)

d) \(2-5\sqrt{x}=-13\)

\(\Leftrightarrow5\sqrt{x}=2+13\)

\(\Leftrightarrow5\sqrt{x}=15\)

\(\Leftrightarrow\sqrt{x}=\dfrac{15}{5}\)

\(\Leftrightarrow\sqrt{x}=3\)

\(\Leftrightarrow x=3^2=9\left(tm\right)\)

a: căn 5<căn 9=3

=>4*căn 5<4*3=12

b: 9=căn 81<căn 85

c: -13=-căn 169<-căn 167

d: căn 13<căn 16=4

=>4+căn 13<8

k: 12=căn 144>căn 134

g: -18=-6*3=-6*căn 9<-6*căn 7

2:

a: A={x∈N|1<=x<=5}

b: B={x∈N|x<=4}

c: C={x∈N*|x<=4}

d: D={x∈N|x chia hết 2; x<10}

e: E={x∈N|x ko chia hết cho 2; x<50}

f: F={x∈N|x chia hết cho 11; x<100}

3:

a: A={4}

=>Có 1 phần tử

b: B={0;1}

=>Có 2 phần tử

c: C=∅

=>Ko có phần tử

d: D={0}

=>Có 1 phần tử

e: E=N

=>Có vô số phần tử

\(\dfrac{12^3\cdot18^2}{24^2}\)

\(=\dfrac{3^3\cdot4^3\cdot9^2\cdot2^2}{4^2\cdot3^2\cdot2^2}\)

\(=\dfrac{3^3\cdot2^6\cdot3^4\cdot2^2}{2^4\cdot3^2\cdot2^2}\)

\(=\dfrac{3^7\cdot2^8}{3^2\cdot2^6}\)

\(=\dfrac{3^5\cdot2^2}{1\cdot1}\)

\(=972\)

3:

a: x^2=15

=>\(x=\pm\sqrt{15}\)

b: x^2=121

=>x=11 hoặc x=-11

c: (x-2)^2=9

=>(x-2-3)(x-2+3)=0

=>(x-5)(x+1)=0

=>x=5 hoặcx=-1

d: =>x+6=15 hoặc x+6=-15

=>x=-21 hoặc x=9

`@` `\text {Ans}`

`\downarrow`

`3,8 * 2x = 1/4*8/3`

`=> 3,8*2x = 2/3`

`=> 2x = 2/3 \div 3,8`

`=> 2x = 10/57`

`=> x = 10/57 \div 2`

`=> x = 5/57`

Vậy, `x = 5/57.`

Mình làm lại theo yc nhé

`3,8 \div 2x = 1/4 \div 8/3`

`=> 3,8*8/3 = 2x*1/4`

`=> 152/15 = 2x*1/4`

`=> 2x = 152/15 \div 1/4`

`=> 2x = 608/15`

`=> x = 608/15 \div 2`

`=> x = 304/15`

Vậy, `x = 304/15.`

Chữ số hàng chục là 8