1) (x+y-2c)(x+y+2c)=(x+y)²-(2c)²=(x+y)²-4c².
2)(a+1)(a+2)(a-1)(a+2)=(a+2)²*(a²-1).
3) (a+b)+x*(a+b)²+y*(a+b)³=(a+b)(1+x*(a+b)+y*(a+b)²).
15х-12-4х-8=2
15х-4х=2+12+8
11х=22
х= 22/11
х= 2
Lg29000=lg29*1000=lg29+lg1000=1.462*-3=-4.386
lg2.9=lg29*0.1=lg29+lg0.1=1.462*-1=-1.462
lg0.29=lg29*0.01=lg29+lg0.01=1.462*-2=-2.924