1C 2D 3A =))

Tính giá trị biểu thức a x 12 + 2,1 x b + 5 với a = 19,36 và b = 7,9 ?

Đáp số: 

`@` `\text {Ans}`

`\downarrow`

`B(x)-A(x)+C(x)`

`=`\((x^2-5x^3-4x+7) - (-x^3 + 7x^2 +2x - 15) + 3x^3 - 7x^2 -4\)

`=`\(x^2-5x^3-4x+7+x^3-7x^2-2x+15+3x^3-7x^2-4\)

`=`\(\left(-5x^3+x^3+3x^3\right)+\left(x^2-7x^2-7x^2\right)+\left(-4x-2x\right)+\left(7+15-4\right)\)

`=`\(-x^3-13x^2-6x+18\)

`C(x)-B(x)-A(x)`

`=`\(3x^3 - 7x^2 -4 - (x^2-5x^3-4x+7) - (-x^3 + 7x^2 +2x - 15)\)

`=`\(3x^3-7x^2-4-x^2+5x^3+4x-7+x^3-7x^2-2x+15\)

`=`\(\left(3x^3+5x^3+x^3\right)+\left(-7x^2-x^2-7x^2\right)+\left(4x-2x\right)+\left(-4-7+15\right)\)

`=`\(9x^3-15x^2+2x+4\)

a) \(B\left(x\right)-A\left(x\right)+C\left(x\right)\)

\(=\left(x^2-5x^3-4x+7\right)-\left(-x^3+7x^2+2x-15\right)+\left(3x^3-7x^2-4\right)\)

\(=x^2-5x^3-4x+7+x^3-7x^2-2x+15+3x^3-7x^2-4\)

\(=\left(-5x^3+x^3+3x^3\right)+\left(x^2-7x^2-7x^2\right)-\left(4x+2x\right)+\left(7-4+15\right)\)

\(=-x^3-13x^2-6x+18\)

b) \(C\left(x\right)-B\left(x\right)-A\left(x\right)\)

\(=\left(3x^3-7x^2-4\right)-\left(x^2-5x^3-4x+7\right)-\left(-x^3+7x^2+2x-15\right)\)

\(=3x^3-7x^2-4-x^2+5x^3+4x-7+x^3-7x^2-2x+15\)

\(=\left(3x^3+5x^3+x^3\right)-\left(7x^2+x^2+7x^2\right)+\left(4x-2x\right)-\left(4+7-15\right)\)

\(=9x^3-15x^2+2x+4\)

\(B\left(x\right)-A\left(x\right)+C\left(x\right)\)

\(=\left(x^2-5x^3-4x+7\right)-\left(-x^3+7x^2+2x-15\right)+\left(3x^3-7x^2-4\right)\)

\(=x^2-5x^3-4x+7+x^3-7x^2-2x+15+3x^3-7x^2-4\)

\(=\left(-5x^3+x^3+3x^3\right)+\left(x^2-7x^2-7x^2\right)+\left(-4x-2x\right)+\left(7+15-4\right)\)

\(=-x^3-13x^2-6x+18\)

\(C\left(x\right)-B\left(x\right)-A\left(x\right)\)

\(=\left(3x^3-7x^2-4\right)-\left(x^2-5x^3-4x+7\right)-\left(-x^3+7x^2+2x-15\right)\)

\(=3x^3-7x^2-4-x^2+5x^3+4x-7+x^3-7x^2-2x+15\)

\(=\left(3x^3+5x^3+x^3\right)+\left(-7x^2-x^2-7x^2\right)+\left(4x-2x\right)+\left(-4-7+15\right)\)

\(=9x^3-15x^2+2x+4\)

Bài 9: 

a: \(A=-0.5x^2yz\cdot\left(-3\right)xy^3z=1.5x^3y^4z^2\)

b: Hệ số là 1,5

Bậc là 9

a, =

b,>

c,>

D

D

D. 109 x (7 + 3)

\(a,x=\dfrac{4}{5}\times\dfrac{1}{3}=\dfrac{4}{15}\)

\(b,x=\dfrac{7}{9}\times\dfrac{3}{5}=\dfrac{7}{15}\)

\(c,x=\dfrac{7}{6}\times\dfrac{4}{3}=\dfrac{14}{9}\\ d,x=\dfrac{9}{7}\times\dfrac{8}{4}=\dfrac{18}{7}\)

X=4/15

X=7/15

X=14/9

X=18/7

a,x:1/3=4/5

x          =4/5.1/3

x          =4/15

b,x:3/5=7/9

x         =7,9.3/5

x         =7/15

c,x.3/4=7/6

x         =7/6:3/4

x         = 14/9

d,4/8.x=9.7

x         =9/7:4/8

x         =18/7

`@` `\text {Ans}`

`\downarrow`

`a,`

`2/5 + x = 2/7`         

`=> x = 2/7 -2/5`

`=> x= - 4/35`

Vậy, `x=-4/35`

`b,`

`x + 3/5 = -2/5`

`=> x = -2/5 - 3/5`

`=> x=-1`

Vậy, `x=-1`

`c, `

`x - 8/5 = 3/7`

`=> x=3/7 + 8/5`

`=> x=71/35`

Vậy, `x=71/35`

`d,`

`3/5 - x = 7/3`

`=> x=3/5 - 7/3`

`=> x=-26/15`

Vậy, `x=-26/15`

a) \(\dfrac{2}{5}+x=\dfrac{2}{7}\)

\(\Rightarrow x=\dfrac{2}{7}-\dfrac{2}{5}\)

\(\Rightarrow x=-\dfrac{4}{35}\)

b) \(x+\dfrac{3}{5}=-\dfrac{2}{5}\)

\(\Rightarrow x=-\dfrac{2}{5}-\dfrac{3}{5}\)

\(\Rightarrow x=-1\)

c) \(x-\dfrac{8}{5}=\dfrac{3}{7}\)

\(\Rightarrow x=\dfrac{3}{7}+\dfrac{8}{5}\)

\(\Rightarrow x=\dfrac{71}{35}\)

d) \(\dfrac{3}{5}-x=\dfrac{7}{3}\)

\(\Rightarrow x=\dfrac{3}{5}-\dfrac{7}{3}\)

\(\Rightarrow x=-\dfrac{26}{15}\)

\(a,\dfrac{2}{5}+x=\dfrac{2}{7}\\ x=\dfrac{2}{7}-\dfrac{2}{5}\\ x=\dfrac{10}{35}-\dfrac{14}{35}\\ x=\dfrac{4}{35}\\ b,x+\dfrac{3}{5}=\dfrac{-2}{5}\\ x=\dfrac{-2}{5}-\dfrac{3}{5}\\ x=\dfrac{-5}{5}\\ x=-1\\ c,x-\dfrac{8}{5}=\dfrac{3}{7}\\ x=\dfrac{3}{7}+\dfrac{8}{5}\\ x=\dfrac{15}{35}+\dfrac{56}{35}\\ x=\dfrac{71}{35}\\ d,\dfrac{3}{5}-x=\dfrac{7}{3}\\ x=\dfrac{3}{5}-\dfrac{7}{3}\\ x=\dfrac{9}{15}-\dfrac{35}{15}\\ x=\dfrac{-26}{15}\)

1/3 x 3/5 x 5/7 x 7/9 x 9/11

= 1 x 3 x 5 x 7 x 9/ 3 x 5 x 7 x 9 x 11

= 1 x 11

= 11

\(A=\frac{1}{3}x\frac{3}{5}x\frac{5}{7}x\frac{7}{9}x\frac{9}{11}\)

\(\Rightarrow A=\frac{1x3x5x7x9}{3x5x7x9x11}\)

\(\Rightarrow A=\frac{1}{11}\)

Vậy A = \(\frac{1}{11}\)

Bài này áp dụng cách trực tiêu của phân số nha!

Chúc em học tốt nhé!!!

mik nhầm đoạn cuối

= 1/11