2A=2⁵¹-2⁵⁰+2⁴⁹-2⁴⁸+...+2³-2²+2

=>2A+A=2⁵¹-2⁵⁰+2⁴⁹-2⁴⁸+...+2³-2²+2+2⁵⁰-2⁴⁹+2⁴⁸-2⁴⁷+...+2²-2+1

=>3A=2⁵¹-1

=>A=\(\frac{2^{51}-1}{3}\)

a,87^2 + 26.87 +13^2

=87.(87+26) + 13^2

=87.113 + 169

=10000

a) \(87^2+26\cdot87+13^2=87^2+2\cdot87\cdot13+13^2=\left(87+13\right)^2=100^2=10000\)

1.
A= \(2\sqrt{6}\) + \(6\sqrt{6}\) - \(8\sqrt{6}\)
A= 0
2.
A= \(12\sqrt{3}\) + \(5\sqrt{3}\) - \(12\sqrt{3}\)
A= 0
3.
A= \(3\sqrt{2}\) - \(10\sqrt{2}\) + \(6\sqrt{2}\)
A= -\(\sqrt{2}\)
4.
A= \(3\sqrt{2}\) + \(4\sqrt{2}\) - \(\sqrt{2}\)
A= \(6\sqrt{2}\)
5.
M= \(2\sqrt{5}\) - \(3\sqrt{5}\) + \(\sqrt{5}\)
M= 0
6.
A= 5 - \(3\sqrt{5}\) + \(3\sqrt{5}\)
A= 5

This literally took me a while, pls sub :D
https://www.youtube.com/channel/UC4U1nfBvbS9y_Uu0UjsAyqA/featured

Ta có : A=(2⁹⁹+2⁹⁸+...+2+1-(2⁴⁹+2⁴⁸+...+2+1)2⁵⁰)/2⁴⁹+2⁴⁸+...+2+1

A= \(\dfrac{2^{99}+2^{98}+...+2+1-2^{99}-2^{98}-...-2^{51}-2^{50}}{2^{49}+2^{48}+...+2+1}\)

A=\(\dfrac{2^{49}+2^{48}+...+2+1}{2^{49}+2^{48}+...+2+1}\) = 1

Vậy đa thức A=1

b, 

\(A=1+2+2^2+2^3+...+2^{50}\)

\(\Rightarrow2A=2+2^2+2^3+...+2^{51}\)

\(\Rightarrow2A-A=2+2^2+2^3+...+2^{51}-1+2+2^2+...+2^{50}\)

\(\Rightarrow A=2^{51}-1\)

mk là nữ nha nói trước đó còn câu đó khó quá