(5y+1)(5y-1)-5(y+25y的2次幂),
=25y²-1-5y-125y²
=-100y²-5y-1
-100(2/5)²-5x2/5-1
=-16-2-1
=-19
（3x+4)(3x-4)<9(x-2)(x+3)
9x²-16<9(x²+x-6)
9x²-16<9x²+9x-54
-9x<-38
x>38/9