6. (x +4)² -(x -2)(x +2), при
x= -0.125
x² +8x +16 -(x² -4) =x² +8x +16 -x² +4 =8x +20 =8*(-0.125) +20 =1 +20 =21
7. 178² -177² =(178 -177)(178 +177) =1*355 =355
8. 25y² -9 =0
(5y -3)(5y +3) =0
5y -3 =0, 5y =3, y =3/5=0.6
5y +3 =0, 5y= -3, y = -0.6
ответ: y= -0.6, y =0.6
9. 125 -8b^3 =5^3 -2^3b^3 =(5 -2b)(5² +5*2b +2²b²) =(5 -2b)(25 +10b +4b²)