tìm giá trị của x để biểu thức nhận giá trị âm nhé

Câu tính bn vít lại đề ik, khó hỉu wa

2) a. x² + 5x = x.(x + 5) âm

=> x.(x + 5) < 0

=> x và x + 5 trái dấu

Mà x < x + 5

=> x < 0; x + 5 > 0

=> x < 0; x > -5

=> x thuộc {-4 ; -3; -2; -1}

b. 3.(2x + 3).(3x - 3)

= 3.(2x + 3).3.(x - 1)

= 9.(2x + 3).(x - 1) âm

=> 9.(2x + 3).(x - 1) < 0

=> (2x + 3).(x - 1) < 0

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

Mà 2x + 3 > 2x - 2

=> 2x + 3 > 0; 2x - 2 < 0

=> 2x > -3; 2x < 2

=>x > -3/2; x < 1

=> x > -2; x < 1

=> x thuộc {-1; 0}

\(\left(\left(\frac{2}{193}-\frac{3}{386}\right).\frac{193}{17}+\frac{33}{34}\right):\left(\left(\frac{7}{1931}+\frac{11}{3862}\right).\frac{1935}{25}+\frac{9}{2}\right)\)

\(=\left(\left(\frac{4}{386}-\frac{3}{386}\right)\frac{193}{17}+\frac{33}{34}\right):\left(\left(\frac{14}{3862}+\frac{11}{3862}\right).\frac{1935}{25}+\frac{9}{2}\right)\)

\(=\left(\frac{1}{386}.\frac{193}{17}+\frac{33}{34}\right):\left(\frac{25}{3862}.\frac{1935}{25}+\frac{9}{2}\right)\)

\(=\left(\frac{1}{34}+\frac{33}{34}\right):\left(\frac{1}{2}+\frac{9}{2}\right)\)

\(=1:\frac{10}{2}=1.\frac{1}{5}=\frac{1}{5}\)

\(a,\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-\frac{20}{15}+\frac{3}{7}\)

\(=>\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{7}{21}+\frac{3}{7}\right)-\frac{20}{15}\)

\(=>1+\frac{16}{21}-\frac{20}{15}\)

\(=>\frac{37}{21}-\frac{20}{15}\)

\(=>\frac{3}{7}\)

\(b,12-8\cdot\left(\frac{3}{2}\right)^3\)

\(=>12-8\cdot\frac{27}{8}\)

\(=>12-27\)

\(=>-15\)

\(c,\left(\frac{1}{9}\right)^{2005}\cdot9^{2005}-96^2:24^2\)

\(=>\left(\frac{1^{2005}^{ }}{9^{2005}}\cdot9^{2005}\right)-\left(96^2:24^2\right)\)

\(=>\left(1^{2005}\right)-16\)

\(=>1-16\)

\(=>-15\)

a) \(\left(\dfrac{1}{6}+\dfrac{5}{9}\right)+\dfrac{4}{9}\)

\(=\dfrac{1}{6}+\dfrac{5}{9}+\dfrac{4}{9}\)

\(=\dfrac{1}{6}+1\)

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

b) \(\dfrac{3}{17}+\left(\dfrac{14}{17}-\dfrac{2}{3}\right)\)

\(=\dfrac{3}{17}+\dfrac{14}{17}-\dfrac{2}{3}\)

\(=1-\dfrac{2}{3}\)

\(=\dfrac{1}{3}\)

c) \(\left(\dfrac{3}{2}-\dfrac{2}{3}\right)+\dfrac{7}{6}\)

\(=\left(\dfrac{9}{6}-\dfrac{4}{6}\right)+\dfrac{7}{6}\)

\(=\dfrac{13}{6}+\dfrac{7}{6}\)

\(=\dfrac{20}{6}\)

bạn ấn vào đúng 0 sẽ ra kết quả, mình làm bài này rồi dễ lắm

b: \(B=\dfrac{x^2-3x+2x^2+6x-3x^2-9}{x^2-9}=\dfrac{3x-9}{\left(x-3\right)\left(x+3\right)}=\dfrac{3}{x+3}\)

b: \(B=\dfrac{x^2-3x+2x^2+6x-3x^2-9}{\left(x-3\right)\left(x+3\right)}\)

\(=\dfrac{3x-9}{\left(x-3\right)\left(x+3\right)}=\dfrac{3}{x+3}\)