\(\left(2x-1\right)^2+\left(x+3\right)^2-5x.\left(x+7\right).\left(x-7\right)\)

( x + 1 ) ^ 2 - ( x-1)^2-3.(x+1).(x-1)

bạn hãy tin mik 100% c)

\(\frac{y+5}{7-y}=\frac{2}{5}\Leftrightarrow5\left(y+5\right)=2\left(7-y\right)\)

5y + 25 = 14 - 2y

2y - 5y = 25 - 14

-3y = 11

y = -11/3

Vậy không có số nguyên y thõa mãn 

x=-2,500620501

\(x+3^2=x^2+2.x.3+3^2=x^2+6x+9\)

\(4x^{^{ }2}-9=4x^2-2.4x.9+9^2=16x^2-72x+81\)

\(\left(x-\dfrac{3}{2}\right)^2=x^2-2.x.\dfrac{3}{2}+\dfrac{3}{2}^2=x^2-3x+\dfrac{9}{4}\)