`(x-10)^2-x(x+80)`

`= x^2-20x+100-x^2-80x`

`= -100x+100`

`= -100*0.98+100`

`= -98+100`

`= 2`

`----`

`(2x+9)^2-x(4x+31)`

`= 4x^2+36x+81-4x^2-31x`

`= 5x+81`

`= 5*(-16.2)+81`

`= -81+81`

`= 0`

`----`

`4x^2-28x+49`

`= (2x)^2-2*2x*7+7^2`

`= (2x-7)^2`

`= (2*4-7)^2`

`= 1^2=1`

`----`

`x^3-9x^2+27x-27`

`= x^3-3*x^2*3+3x*3^2-3^3`

`= (x-3)^3`

`= (5-3)^3`

`= 2^3=8`

`----`

`9x^2+42x+49`

`= (3x)^2+2*3x*7+7^2`

`= (3x+7)^2`

`= (3*1+7)^2`

`= 10^2=100`

`----`

`25x^2-2xy+1/25y^2`

`= (5x)^2-2*1/5y*5x+(1/5y)^2`

`= (5x-1/5y)^2`

`= [5(-1/5)-1/5(-5)]^2`

`= (-1+1)^2`

`= 0^2=0`

`----`

`27+(x-3)(x^2+3x+9)`

`= 27+x^3-3^3`

`= 27+x^3-27`

`= x^3`

`= (-3)^3`

`= -27`

`----`

`x^3+3x^2+3x+1`

`= x^3+3*x^2*1+3x*1+1^3`

`= (x+1)^3`

`= (99+1)^3`

`= 100^3`

`= 1000000`

`tt(#Zero  X)`