A= 49x^2-70x+25
Khi x=5 => A= 49 . 5^2 - 70 . 5 + 25
A= 49 . 25 - 350 + 25
A= 1225 + 350 + 25
A= 1600
Khi x=1/7 => A= 49 . ( 1/7 ) ^2 - 70 . 1/7 +25
A= 49 . 1/49 - 10 + 25
A= 1 - 10 + 25
A= 16
A = 49x^2 - 70x + 25
= (7x)^2 - 2* 7 x * 5 + 5^2
= (7x - 5)^2
Khi x= 5 , A= (7 * 5 -5)^2
= 30^2
= 900
Khi x=1/7, A = (7* 1/7 - 5)^2
= (-4)^2
= 16
Vậy khi x= 5, A= 900
khi x= 1/7, A= 16
A= 49x^2-70x+25
Khi x=5 => A= 49 . 5^2 - 70 . 5 + 25
A= 49 . 25 - 350 + 25
A= 1225 + 350 + 25
A= 1600
Khi x=1/7 => A= 49 . ( 1/7 ) ^2 - 70 . 1/7 +25
A= 49 . 1/49 - 10 + 25
A= 1 - 10 + 25
A= 16
A= 49x^2-70x+25
Khi x=5 => A= 49 . 5^2 - 70 . 5 + 25
A= 49 . 25 - 350 + 25
A= 1225 + 350 + 25
A= 1600
Khi x=1/7 => A= 49 . ( 1/7 ) ^2 - 70 . 1/7 +25
A= 49 . 1/49 - 10 + 25
A= 1 - 10 + 25
A= 16
\(A=49x^2-70x+25=\left(7x\right)^2-2\times5\times7x+5^2=\left(7x-5\right)^2\)
Khi \(x=5\) thì \(A=\left(7\times5-5\right)^2=30^2=900\)
Khi \(x=\frac{1}{7}\)thì \(A=\left(7\times\frac{1}{7}-5\right)^2=\left(-4\right)^2=16\)