Ta có : (x + 7)⁶ \(\ge0\forall x\)

=> A = (x + 7)⁶ - 21 \(\ge-21\)

Dấu "=" xảy ra <=> x + 7 = 0

=> x =- 7

Vạy Min A = -21 <=> x = -7

b) Ta có -4(8 - x)⁸ \(\le0\)

=> 26 - 4(8 - x)⁸ \(\le26\)

Dấu "=" xảy ra <=> 8 - x = 0 

<=> x = 8

Vậy Max B = 26 <=> x = 8

d, \(-16+\left(5-x\right)^4=0\Leftrightarrow\left(x-5\right)^4=16\)

TH1 : \(x-5=2\Leftrightarrow x=7\)

TH2 : \(x-5=-2\Leftrightarrow x=3\)

e, \(24-\left(x+9\right)^3=32\Leftrightarrow\left(x+9\right)^3=-8=\left(-2\right)^3\)

\(\Leftrightarrow x+9=-2\Leftrightarrow x=-11\)

g, \(\left(x+3\right)^4-5=-7\Leftrightarrow\left(x+3\right)^4=-2\)( vô lí )

do \(\left(x+3\right)^4\ge0\forall x;-2< 0\)

h, \(4^x+4^{x+2}=272\Leftrightarrow4^x\left(1+4^2\right)=272\)

\(\Leftrightarrow4^x=16\Leftrightarrow4^x=4^2\Leftrightarrow x=2\)

2 ^332 < 3 ^223

\(2^{225}=\left(2^3\right)^{75}=8^{75}\)

\(3^{150}=\left(3^2\right)^{75}=9^{75}\)

\(8^{75}< 9^{75}\Rightarrow2^{225}< 3^{150}\)

\(2^{91}=\left(2^7\right)^{13}=128^{13}\)

\(5^{35}< 5^{36}=\left(5^3\right)^{12}=125^{12}\)

\(\Rightarrow2^{91}=128^{13}>128^{12}>125^{12}=5^{36}>5^{35}\)

bằng nhau nhé bạn 

hok tốt