`#Sad`
`(5x+2)^2+(4x-3)^2+2(5x-2)(5x+2)-75x+2`
`= 25x^2+20x+4+16x^2-24x+9+2(25x^2-4)-75x+2`
`= 25x^2+20x+4+16x^2-24x+9+50x^2-8-75x+2`
`= (25x^2+16x^2+50x^2)+(20x-24x-75x)+(4+9-8+2)`
`= 91x^2-79x+7`
`\text{→Áp dụng:}`
`+)` `(A+B)^2 = A^2+2AB+B^2`
`+)` `(A-B)^2 = A^2-2AB+B^2`
`+)` `A^2-B^2 = (A-B)(A+B)`