1. a

2. c

D. \(\dfrac{1}{x}\)

Câu 9:

Chiều rộng hình chữ nhật là: 150 : 50 = 3 (m)

Diện tích hình tam giác MDC là:

\(3\times50:2=75\left(m^2\right)\)

a) \(5x-2=3x+8\)

\(\Leftrightarrow5x-3x=8+2\)

\(\Leftrightarrow2x=10\)

\(\Leftrightarrow x=5\)

Vậy S = {5}

b) \(\dfrac{x+1}{2}+\dfrac{3x-2}{3}=\dfrac{x-7}{12}\)

\(\Leftrightarrow\dfrac{6\left(x+1\right)}{12}+\dfrac{4\left(3x-2\right)}{12}=\dfrac{x-7}{12}\)

\(\Leftrightarrow6x+6+12x-8=x-7\)

\(\Leftrightarrow6x+12x-x=-7-6+8\)

\(\Leftrightarrow17x=-5\)

\(\Leftrightarrow x=-\dfrac{5}{17}\)

Vậy \(S=\left\{-\dfrac{5}{17}\right\}\)

c) \(\left(x-4\right)\left(7x-3\right)-x^2+16=0\)

\(\Leftrightarrow7x^2-3x-28x+12-x^2+16=0\)

\(\Leftrightarrow6x^2-31x+28=0\)

\(\Leftrightarrow6x^2-24x-7x+28=0\)

\(\Leftrightarrow\left(6x^2-24x\right)-\left(7x-28\right)=0\)

\(\Leftrightarrow6x\left(x-4\right)-7\left(x-4\right)=0\)

\(\Leftrightarrow\left(x-4\right)\left(6x-7\right)=0\)

\(\Leftrightarrow x-4=0;6x-7=0\)

*) \(x-4=0\)

\(\Leftrightarrow x=4\)

*) \(6x-7=0\)

\(\Leftrightarrow6x=7\)

\(\Leftrightarrow x=\dfrac{7}{6}\)

Vậy \(S=\left\{\dfrac{7}{6};4\right\}\)

d) \(\dfrac{2x}{x-3}-\dfrac{5}{x+3}=\dfrac{x^2+21}{x^2-9}\)     (1)

ĐKXĐ: \(x\ne3;x\ne-3\)

MTC: \(x^2-9\)

\(\left(1\right)\Leftrightarrow2x\left(x+3\right)-5\left(x-3\right)=x^2+21\)

\(\Leftrightarrow2x^2+6x-5x+15-x^2-21=0\)

\(\Leftrightarrow x^2+x-6=0\)

\(\Leftrightarrow x^2+2x-3x-6=0\)

\(\Leftrightarrow\left(x^2+2x\right)-\left(3x+6\right)=0\)

\(\Leftrightarrow x\left(x+2\right)-3\left(x+2\right)=0\)

\(\Leftrightarrow\left(x+2\right)\left(x-3\right)=0\)

\(\Leftrightarrow x+2=0;x-3=0\)

*) \(x+2=0\)

\(x=-2\) (nhận)

*) \(x-3=0\)

\(x=3\) (loại)

Vậy \(S=\left\{-2\right\}\)

a) Đ

b) S

Var a,b:integer;

Begin

Write('Nhap a = ');readln(a);

Write('Nhap b = ');readln(b);

If a >= b then write(b,'   ;   ', a)

Else write(a,'   ;   ',b);

Readln;

End.