Упростите выражения:
1) (x+2)(x-5)-3x(1-2x)
x^2-5x+2x-10-3x+6x^2=7x^2-6x-10
2) (a+3)(a-2)+(a-3)(a+6)
a^2-2a+3a-6+a^2+6a-3a-18=
2a^2+4a-24=a^2+2a-12
3) (x-7)(3x-2)-(5x+1)(2x-4)
3x^2-2x-21x+14-(10x^2-20x+2x-4)=
3x^2-23x+14-10x^2+18x-4=
-7x^2-5x+10
4) (5x-2y)(3x+5y)-(2,5x-3y)(4x+8y)
15x^2+25xy-6xy-10y^2-(10x^2+20xy-12xy-24y^2)=
15x^2+19xy-10y^2-10x^2-8xy+24y^2=
5x^2+14y^2+11xy
5) (3a²+5y)(2a³+y)-7a³(a²-3y)
6a^5+3a^2y+10a^3y+5y^2-7a^5+21a^3y=
-a^5+3a^2y+31a^3y+5y^2