mờ quá

Lỗi r, xem lại nha

Câu 4:

Var a:array[1..1000] of integer;

s:longint;

i,n:integer;

Begin

Write('n = ');readln(n);

For i:=1 to n do

Begin

Write('Nhap so thu ',i);readln(a[i]);

If a[i] > 0 then s:=s+a[i];

End;

Write('Tong la ',s);

Readln

End.

Câu 1

Var a:array[1..1000] of real;

s:real;

i,n:integer;

Begin

Write('n = ');readln(n);

s:=1;

For i:=1 to n do

Begin

Write('Nhap so thu ',i);readln(a[i]);

If a[i] > 0 then s:=s*a[i];

End;

Write('Tich la ',s:10:2);

Readln

End.

Câu 5:

Var a:array[1..1000] of integer;

min,i,n:integer;

Begin

Write('n = ');readln(n);

For i:=1 to n do

Begin

Write('Nhap so thu ',i);readln(a[i]);

End;

min:=a[1];

For i:=2 to n do

If min > a[i] then min:=a[i];

Write('So nho nhat la ',min);

Readln

End.

5. 

ĐKXĐ: \(cos\left(x-30^0\right)\ne0\Leftrightarrow x\ne120^0+k180^0\)

Pt tương đương:

\(\left[{}\begin{matrix}tan\left(x-30^0\right)=0\\cos\left(2x-150^0\right)=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x-30^0=k180^0\\2x-150^0=90^0+k180^0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=30^0+k180^0\\x=120^0+k90^0\end{matrix}\right.\)

Kết hợp ĐKXĐ: \(\Rightarrow x=30^0+k180^0\)

6.

\(\Leftrightarrow2\sqrt{2}sinx.cosx+2cosx=0\)

\(\Leftrightarrow2cosx\left(\sqrt{2}sinx+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}cosx=0\\sinx=-\dfrac{\sqrt{2}}{2}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{2}+k\pi\\x=-\dfrac{\pi}{4}+k2\pi\\x=\dfrac{5\pi}{4}+k2\pi\end{matrix}\right.\)

5. \(\Leftrightarrow\left[{}\begin{matrix}\tan\left(x-30\right)=0\\\cos\left(2x-150\right)=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x-30=360k\\\left[{}\begin{matrix}2x-150=90+360k\\2x-150=270+360k\end{matrix}\right.\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=30+360k\\x=120+180k\\x=210+180k\end{matrix}\right.\)

Vậy ...

6, \(\Leftrightarrow2\sqrt{2}\sin x.\cos x+2\cos x=0\)

\(\Leftrightarrow\cos x\left(1+\sqrt{2}\sin x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}\cos x=0\\\sqrt{2}\sin x+1=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}x=\dfrac{\pi}{2}+k2\pi\\x=\dfrac{3}{2}\pi+k2\pi\end{matrix}\right.\\x=-\dfrac{\pi}{4}+k2\pi\\x=\dfrac{7}{4}\pi+k2\pi\end{matrix}\right.\)

Vậy ...

18.

Do D thuộc trục hoành nên tọa độ có dạng: \(D\left(a;0;0\right)\)

\(\Rightarrow\left\{{}\begin{matrix}\overrightarrow{AD}=\left(a-3;4;0\right)\\\overrightarrow{BC}=\left(4;0;-3\right)\end{matrix}\right.\)

\(AD=BC\Leftrightarrow\left(a-3\right)^2+4^2=4^2+\left(-3\right)^2\)

\(\Rightarrow\left(a-3\right)^2=9\Rightarrow\left[{}\begin{matrix}a=0\\a=6\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}D\left(0;0;0\right)\\D\left(6;0;0\right)\end{matrix}\right.\)

19.

\(cos\left(\overrightarrow{a};\overrightarrow{b}\right)=\dfrac{2.\left(-1\right)+1.0+0.\left(-2\right)}{\sqrt{2^2+1^2+0^2}.\sqrt{\left(-1\right)^2+0^2+\left(-2\right)^2}}=-\dfrac{2}{5}\)

20.

\(\overrightarrow{OA}=\left(2;2;1\right)\Rightarrow OA=\sqrt{2^2+2^2+1^2}=3\)

1.\(x^2+4x+4=\left(x+2\right)^2\)

2.\(x^2-8x+16=\left(x-4\right)^2\)

3.\(\left(x+5\right)\left(x-5\right)=x^2-25\)

4.\(x^3+12x+48x+64=\left(x+4\right)^3\)

5.\(x^3-6x^2+12x-8=\left(x-2\right)^3\)

6.\(\left(x+2\right)\left(x^2-2x+4\right)=x^3+8\)

7.\(\left(x-3\right)\left(x^2+3x+9\right)=x^3-27\)

8.\(4x^4-15=\left(2x^2\right)^2-\left(\sqrt{15}\right)^2=\left(2x^2-\sqrt{15}\right)\left(2x^2+\sqrt{15}\right)\)