b) 5( 2x + 3 )( x + 2 ) - 2( 5x - 4 )( x - 1 ) = 75

<=> 5( 2x² + 7x + 6 ) - 2( 5x² - 9x + 4 ) = 75

<=> 10x² + 35x + 30 - 10x² + 18x - 8 = 75

<=> 53x + 22 = 75

<=> 53x = 53

<=> x = 1

c) 2x² + 3( x - 1 )( x + 1 ) = 5x( x + 1 )

<=> 2x² + 3( x² - 1 ) = 5x² + 5x

<=> 2x² + 3x² - 3 - 5x² - 5x = 0

<=> -3 - 5x = 0

<=> -5x = 3

<=> x = -3/5

b, \(5\left(2x+3\right)\left(x+2\right)-2\left(5x-4\right)\left(x-1\right)=75\)

\(\Leftrightarrow10x^2+20x+15x+30-10x^2+10x+8x-8=75\)

\(\Leftrightarrow53x+22=75\Leftrightarrow x=1\)

c, \(2x^2+3\left(x-1\right)\left(x+1\right)=5x\left(x+1\right)\)

\(\Leftrightarrow2x^2+3x^2+3x-3x-3=5x^2+5x\)

\(\Leftrightarrow5x^2-3=5x^2+5x\Leftrightarrow x=-\frac{3}{5}\)

=x²y³ - 5x²y³ + \(\dfrac{75}{2}\)x²y³ - 51xy³ - 5xy³ + \(\dfrac{75}{2}\)x²y³

=( x²y³ - 5x²y³ +  \(\dfrac{75}{2}\)x²y³ +  \(\dfrac{75}{2}\)x²y³ ) + ( - 51xy³ - 5xy³)

= 71x²y³ - 56xy³

a: =>x:2,2=15,2x2=30,4

=>x=66,88

b: =>(15/4x+3/4)=-2/3

=>15/4x=-17/12

hay x=-17/45

a) 3(1-4x) (x-1) +4(3x-2) (x+3)=-27
b) 5(2x+3) (x+2)-2(5x-4) (x-1)=75

\(90-5\times\left(x+1\right)=75\)

\(\Rightarrow5\left(x+1\right)=15\)

\(\Rightarrow x+1=3\)

\(\Rightarrow x=2\)

\(90-5\times\left(x+1\right)=75.\)

             \(5\times\left(x+1\right)=90-75\)

             \(5\times\left(x+1\right)=15\)

                         \(x+1=15:5\)

                         \(x+1=3\)

     \(\Rightarrow x=2\)

90 - 5 x (X + 1) = 75

5 x (X + 1)        = 90 - 75

x + 1                 = 15 : 5

x                       = 3 - 1

x                       = 2

a) 4x - 15 = -75 - x

5x - 15 = -75 ( thêm 2 vế mỗi vế 1x )

5x = -75 + 15

5x = -60

x = -60 : 5

x = -12

b) 72 - 3x = 5x + 3

72 = 8x + 3

72 - 3 = 8x

69 = 8x

x = 69 : 8

x = 8,625

tự mà làm bài đó dễ mà

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