862. Преобразуйте выражение: a) (2x+3)²; б) (10+8k)²; в) (5a+b)²; г) (0,3x-0,5a)²; д) (7y-6)²; е) (5y-4x)²; ж) (m-2n)²; з) (10c+0,1y)²

а)
[
(2x+3)^2=(2x)^2+2\cdot2x\cdot3+3^2=4x^2+12x+9.
]

б)
[
(10+8k)^2=10^2+2\cdot10\cdot8k+(8k)^2=100+160k+64k^2.
]

в)
[
(5a+b)^2=(5a)^2+2\cdot5a\cdot b+b^2=25a^2+10ab+b^2.
]

г)
[
(0{,}3x-0{,}5a)^2=(0{,}3x)^2-2\cdot0{,}3x\cdot0{,}5a+(0{,}5a)^2
]
[
=0{,}09x^2-0{,}3ax+0{,}25a^2.
]

д)
[
(7y-6)^2=(7y)^2-2\cdot7y\cdot6+6^2=49y^2-84y+36.
]

е)
[
(5y-4x)^2=(5y)^2-2\cdot5y\cdot4x+(4x)^2
]
[
=25y^2-40xy+16x^2.
]

ж)
[
(m-2n)^2=m^2-2\cdot m\cdot2n+(2n)^2=m^2-4mn+4n^2.
]

з)
[
(10c+0{,}1y)^2=(10c)^2+2\cdot10c\cdot0{,}1y+(0{,}1y)^2
]
[
=100c^2+2cy+0{,}01y^2.
]