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1 Products are advertised mainly through the media so that consumers become familiar with the variety of products available

2 Large companies employ advertising agencies so as to make their product attractive to consumers

3 Companies spend millions of dollars on advertising with the aim of increasing their sales

4 Advertisers must consider their advertisements carefully for fear of being accused of persuading people to buy things they don't need

5 All advertisement are reviewed by a consumer protection agency in case false information is given to the public

Bài 1:

a. $=2x(x-3)$

b. $=x^3(x+3)+(x+3)=(x^3+1)(x+3)=(x+1)(x^2-x+1)(x+3)$

c. $=64-(x^2-2xy+y^2)=8^2-(x-y)^2$

$=(8-x+y)(8+x-y)$

Bài 2:

$(x+5)(x+1)+(x-2)(x^2+2x+4)-x(x^2+x-2)$

$=x^2+6x+5+(x^3-2^3)-(x^3+x^2-2x)$

$=x^2+6x+5+x^3-8-x^3-x^2+2x$

$=8x-3$

Ta có đpcm.

d: =-100+720/718

=-35540/359

e: \(=5^3-9\cdot16=125-144=-19\)

f: \(=8\cdot9-7^2+7=72+7-49=30\)

b: Ta có: \(\left(x+y\right)^2-x^2+4xy-4y^2\)

\(=\left(x+y\right)^2-\left(x-2y\right)^2\)

\(=\left(x+y-x+2y\right)\left(x+y+x-2y\right)\)

\(=3y\cdot\left(2x-y\right)\)

c: Ta có: \(\left(x+y\right)^3-\left(x-y\right)^3\)

\(=x^3+3x^2y+3xy^2+y^3-x^3+3x^2y-3xy^2+y^3\)

\(=2y^3+6x^2y\)

\(=2y\left(3x^2+y^2\right)\)

Chiều rộng là 100:5=20(m)

Chu vi hàng rào là:

\(\left(100+20\right)\cdot2=120\cdot2=240\left(m\right)\)

Số tiền phai trả là:

\(240\cdot300000=72000000\) (đồng)

=>Chọn D