\[\begin{array}{l}
a)A = {(x - 10)^2} - x.(x + 80)\\
voi:x = 0,98\\
A = {x^2} - 20x + 100 - {x^2} - 80x\\
= - 100x + 100\\
Thay:x = 0,98\\
= > A = - 100.0,98 + 100\\
= - 98 + 100\\
= 2\\
b)B = {(2x + 9)^2} - x.(4x + 31)\\
voi:x = - 16,2\\
B = 4{x^2} + 36x + 81 - 4{x^2} - 31x\\
= 5x + 81\\
thay:x = - 16,2\\
= > B = 5.\left( { - 16,2} \right) + 81\\
= - 81 + 81\\
= 0\\
c)C = 4{x^2} - 28x + 49\\
voi:x = 4\\
C = {\left( {2x} \right)^2} - 2.2x.7 + {7^2}\\
= {\left( {2x - 7} \right)^2}\\
Thay:x = 4\\
= > C = {\left( {2.4 - 7} \right)^2}\\
= {1^2} = 1\\
d)D = {x^3} - 9{x^2} + 27x - 27\\
voi:x = 5\\
D = {x^3} - 3.{x^2}.3 + 3.x{.3^2} - {3^3}\\
= {\left( {x - 3} \right)^3}\\
Thay:x = 5\\
= > D = {\left( {5 - 3} \right)^3}\\
= {2^3}\\
= 8\\
e)E = 9{x^2} - 42x + 49\\
voi:x = 1\\
E = {\left( {3x} \right)^2} - 2.3x.7 + {7^2}\\
= {\left( {3x - 7} \right)^2}\\
Thay:x = 1\\
= > E = {\left( {3.1 - 7} \right)^2}\\
= {\left( { - 4} \right)^2}\\
= 16\\
f)F = 25{x^2} - 2xy + \frac{1}{{25}}{y^2}\\
voi:x = - \frac{1}{5},y = - 5\\
F = {\left( {5x} \right)^2} - 2.5x.\frac{1}{5}y + \left( {\frac{1}{5}{y^2}} \right)\\
= {\left( {5x - \frac{1}{5}y} \right)^2}\\
thay:x = - \frac{1}{5},y = - 5\\
= > F = {\left( {5.\frac{{ - 1}}{5} - \frac{1}{5}.\left( { - 5} \right)} \right)^2}\\
= {\left( { - 1 + 1} \right)^2}\\
= {0^2}\\
= 0\\
g)G = 27 + (x - 3).({x^2} + 3x + 9)\\
voi:x = - 3\\
= {3^3} + {x^3} - {3^3}\\
= {x^3}\\
thay:x = - 3\\
= > G = {\left( { - 3} \right)^3}\\
= - 27\\
i)I = {x^3} + 3{x^2} + 3x + 1\\
voi:x = 99\\
= {\left( {x + 1} \right)^3}\\
thay:x = 99\\
= > I = {\left( {99 + 1} \right)^3}\\
= {100^3}\\
= 1000000
\end{array}\]