(2x-7)(x+1)+3(4x-1)(4x+1)=2 (5x-2)²-53 2x²-7x+2x-7+3(16x²-1)=2(25x²-20x +4)-53 2x²-5x-7+48x²-3=50x²-40x+8-53 -5x- 10=-40x-45 35x=-35 x=-1
Log(3)21*log(7)3-log(6)3*log(7)6=log(3)21*1/log(3)7-log(6)3*1/log(6)7=
=log(3)21/log(3)7-log(6)3/log(6)7=log(7)21-log(7)3=log(7)3/21=log(7)1/7=-1