Question

so sánh hai số x và y cho biết 

a) x + 15 > y + 15

b) 13x - 5 < 13y - 5 

c) -21x \(\le\)  -21y

d) -8x + 1 > -8y +1

Answer 1

a: x+15>y+15

=>x+15-15>y+15-15

=>x>y

b: 13x-5<13y-5

=>13x<13y

=>\(\dfrac{13x}{13}< \dfrac{13y}{13}\)

=>x<y

c: -21x<=-21y

=>21x>=21y

=>x>=y

d: -8x+1>-8y+1

=>-8x>-8y

=>8x<8y

=>x<y 

Answer 2

a: x+15>y+15

=>x+15-15>y+15-15

=>x>y

b: 13x-5<13y-5

=>13x<13y

=>\(\dfrac{13x}{13}< \dfrac{13y}{13}\)

=>x<y

c: -21x<=-21y

=>21x>=21y

=>x>=y

d: -8x+1>-8y+1

=>-8x>-8y

=>8x<8y

=>x<y