cũng ko bik lm hả Uyên

vận tốc trung bình của cả 2 quãng đường:

v_tb=\(\dfrac{s_1+s_2}{t_1+t_2}=\dfrac{2+3.25}{1.5+1}=\dfrac{5.25}{2.5}=2.1\dfrac{km}{h}\)

a. (2x+3)³ = (2x)³+3.(2x)².3+3.2x.3²+3³=8x +36x²+54x²+9=8x+90x²+9

b. (2x-3) (4x²+6x+9) = 2x.4x²+2x.6x+2x.9-3.4x²-3.6x-3.9 = 8x³+12x²+18x-12x²-18x-27 = 8x³-27

c. (3x+4y) (9x²-12xy+16y²) = 3x.9x²-3x.12xy+3x.16y²+4y.9x²-4y.12xy+4y.16y²= 27x³-36x²y+48xy²+36x²y-48xy²+64y³

a. (2x-5)³= (2x)³-3.(2x)².5+3.2x.5²-5³ = 8x³-100x²+150-125=8x³-100x²+25

b. (3x+2)² = (3x)²+2.3x.2+2² = 9x²+12x+4

c. (2x-3y)³ = (2x)³-3. (2x)².3y+3.2x.(3y)²-(3y)³=8x-36x²y+54xy²-27y³

^d. (3x-5)²= (3x)²-2.3x.5+2² = 9x²+30x+4