a) x² +x +1 = x² + x + 1/4 + 3/4 =(x+1/2)² + 3/4

=> GTNN a) =3/4 khi x=-1/2

b) 4x² +4x -5 = 4x² + 4x +1 -6 = (2x+1)²-6

=> GTNN b) = -6 khi x=-1/2

c) (x-3)(x+5) +4 = x²+2x -11 = x²+2x +1-12=(x+1)²-12

GTNN c) =12 khi x=-1 

d) x²-4x+y²-8y+6=x²-4x+4+y²-8y+16-14=(x-2)²+(y-4)²-14

GTNN d) =-14 khi x=2 , y=4

S + O₂ → SO₂

n S = 9,6:32 =0,3 = n O₂ = n SO₂ 

m SO2 = 0,3.(32+16.2)=19,2 g

V O2= 0,3.22,4=6,72 lít

diện tích khu đất là 215.215=46225 cm2

Chu vi hình chữ nhật đó là

5.6=30 cm

nửa chu vi hình chữ nhật là 

30:2=15 cm

chiều dài hcn là 

15-5=10 cm

diện tích hcn là 

10.5=50 cm2

begin 

write ('TRUONG THCS ...');

write ('CHAO CAC BAN HOC SINH LOP 8');

readln ;

end.

2⁵ . 4³ = 2⁵ . 2^2.3 = 2⁵ . 2⁶ =2¹¹ =2048

15 I usualy work out at the gym in the morning before i leave for work at eight am 

11 As  Henry need to learn english I will teach him 

12 even though it was raining outside , we went for a walk

13 Yvonne played gold extremely  well when she was very young

14 Because Franklin wants to get a new job , he is preparing for job 

15