1. x = 405

2. y = 1/3

3. x = 37/245

4. 0

1= 405

2 = 67/201

3 = 37/245

4 = 0

C)

x-140:35=270

x-140=270x35

x-140=9450

x=9450+140

x=9590

a) (x + 74) - 318 = 200

x + 74 = 200 + 318

x + 74 = 518

x = 518 - 74

x = 444

b) 3636 : (12.x - 91) = 36

3636 = 36(12.x - 91)

3636 : 36 = 12.x - 91

101 = 12.x - 91

101 + 91 = 12.x

192 = 12.x

192 : 12 = x

16 = x

x = 16

c) x - 140 : 35 = 270

x - 4 = 270

x = 270 + 4

x = 274

\(B=\dfrac{5}{3}x\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+...+\dfrac{1}{90}\right)=\)

\(=\dfrac{5}{3}x\left(\dfrac{1}{1x2}+\dfrac{1}{2x3}+\dfrac{1}{3x4}+\dfrac{1}{4x5}+...+\dfrac{1}{9x10}\right)\)

\(C=\dfrac{2-1}{1x2}+\dfrac{3-2}{2x3}+\dfrac{4-3}{3x4}+...+\dfrac{10-9}{9x10}=\)

\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}=\)

\(=1-\dfrac{1}{10}=\dfrac{9}{10}\)

\(\Rightarrow B=\dfrac{5}{3}xC=\dfrac{5}{3}x\dfrac{9}{10}=\dfrac{3}{2}\)

lấy máy tính tự làm đi

dễ lắm

270*20+58*270+28*270=270*/20+58+28\=270*100=270 

ĐKXĐ:\(x\ne0,x\ne-12\)

\(\dfrac{270}{x}-\dfrac{270}{x+12}=\dfrac{7}{10}\\ \Leftrightarrow270\left(\dfrac{1}{x}-\dfrac{1}{x+12}\right)=\dfrac{7}{10}\\ \Leftrightarrow\dfrac{x+12-x}{x\left(x+12\right)}=\dfrac{7}{2700}\\ \Leftrightarrow\dfrac{12}{x^2+12x}=\dfrac{7}{2700}\\ \Leftrightarrow7x^2+84x-32400=0\)

Xem lại đề

Tổng số công nhân là: 270 : 36 x 100 = 750 (công nhân)

Số công nhân nam : 750 - 270  = 480 (công nhân)

Đáp số :.......

ko bt lm

ĐKXĐ: x∉{0;-2}

Ta có; \(\frac{270}{x+2}+\frac{7}{10}=\frac{270}{x}\)

=>\(\frac{270}{x}-\frac{270}{x+2}=\frac{7}{10}\)

=>\(\frac{270\left(x+2\right)-270x}{x\left(x+2\right)}=\frac{7}{10}\)

=>\(\frac{270x+540-270x}{x\left(x+2\right)}=\frac{7}{10}\)

=>7x(x+2)=5400

=>\(7x^2+14x-5400=0\)

=>\(x^2+2x-\frac{5400}{7}=0\)

=>\(x^2+2x+1-\frac{5407}{7}=0\)

=>\(\left(x+1\right)^2=\frac{5407}{7}\)

=>\(x+1=\pm\sqrt{\frac{5407}{7}}\)

=>\(x=-1\pm\sqrt{\frac{5407}{7}}\) (nhận)