3.
x³+5³=x³+125
4.
2(x²-4)=x²-16+x²-9+x
2x²-8=2x²+x-25
2x²-2x²-x=-25+8
-x= -17
x=17
5.
(2x)³-7³+343-4(4x²-1)=8x³-343+343-16x²+4=8x³-16x²+4
8*(-0.5)³-16*(-0.5)²+4=8*(-1/2)³ - 16*(-1/2)² +4=
=8*(-1/8)-16*(1/4)+4= -1 -4+4= -1
6.
(3-1)(3+1)=3²-1²=3²-1
(3²-1)(3²+1)=3⁴-1
(3⁴-1)(3⁴+1)=3⁸-1
(3⁸-1)(3¹⁶+3⁸+1)=(3⁸)³-1³=3²⁴-1
3²⁴-1-3²⁴= -1