Question

Answer 1

Bài 1:

a. <=> 4x=-20

<=> x= -5

S={-5}

b. <=> 2x+2=5x-7

<=>2x-5x= -7-2

<=> -3x= -9

<=>x=3

S={3}

c. <=> -7x+3x=9-15

<=>-4x=-6

<=>x=\(\dfrac{3}{2}\)

S={\(\dfrac{3}{2}\)}

d. <=> 2x+5x=15-1

<=>7x=14

<=>x=2

S={2}

Answer 2

Bài 2:

a. <=> 2(2x+5)+12=3(3-x)

<=> 4x+10+12=9-3x

<=>4x+3x=9-10-12

<=>7x= -13

<=>x=\(\dfrac{-13}{7}\)

S={\(\dfrac{-13}{7}\)}

b.ĐKXĐ: x khác -1, x khác 0

 <=> x(x+3) + (x-2)(x+1)= 2x(x+1)

<=> x²+3x+ x²+x-2x-2= 2x²+2x

<=> x²+3x+x²+x-2x-2x²-2x= 2

<=> 0x=2

S={vô nghiệm}

c. ĐKXĐ: x khác -2, x khác 2

<=>(x-2)(x+2) +3(x+2)=x²-11

<=> x²+2x-2x-4+2x+6=x²-11

<=>x²+2x-2x+2x-x²=-11+4-6

<=> 2x=-13

<=>x= \(\dfrac{-13}{2}\)

S={\(\dfrac{-13}{2}\)}

d. <=> 2(x-2) - (x+1)= 3x-11

<=> 2x-4 -x-1=3x-11

<=>2x-x-3x=-11+4+1

<=>-2x= -6

<=>x=3

S={3}

Answer 3

Bài 3:

Ta có a>b

=> 2a>2b

=> 5-2a<5-2b