1) (a-3)(a+5) -(2a-5)² =a²+5a-3a-15 -(4a²-20a+25) =a²+2a-15-4a²+20a-25 = -3a² +22a -40
2) 2xy² -18x =2x(y² -9) =2x(y -3)(y +3)
3) x^3 -64x =0
x(x² -64) =0
x=0
x²-64=0, (x-8)(x+8)=0
x-8=0, x=8
x+8=0, x= -8
ответ: x= -8, x=0, x=8
4) x+5=3x+9
x -3x =9-5
-2x =4
x = -2
5) 3b -(5b -1) +(b +4) =3b -5b +1 +b +4 =5 -5b +4b =5 -b