Rút gọn các biểu thức: P = (5x − 1) + 2(1 − 5x)(4 + 5x) + (5x+4)^2

* Hướng dẫn giải

   P = (5x − 1) + 2(1 − 5x)(4 + 5x) + ${\left(5x+4\right)}^2$

      = 5x – 1 + (2 – 10x).( 4+ 5x) + ${\left(5x+4\right)}^2$

      = 5x – 1 + 8 + 10x – 40x – 50$x^2$ + 25$x^2$ + 40x + 16

      = (- 50$x^2$ + 25$x^2$)+ ( 5x + 10x – 40x + 40x) + (- 1+ 8 + 16)

      = -25$x^2$ + 15x + 23