7. Solve the equation for \( x \). \[ \log _{x} 64=\frac{3}{4} \] \( x=\square 16 \) 16 (Type an integer or a simplified fraction.)

\( \frac { 1 } { r } \times \frac { 1 - ( \frac { 1 } { r } ) ^ { n } } { 1 - \frac { 1 } { r } } \geq \frac { 9 r } { 100 } \Rightarrow 1 - \frac { 1 } { r ^ { n } } \geq \frac { 9 r } { 100 } \)

\( f(x)=2 x-1 \) and \( g(x)=3 x^{2} \) Find both \( f \circ g \) and \( g \circ f \), stating domain and range of each.

3. ( 0,5 điểm) Tìm \( x \) biết: \( x^{2}(x-1)+4=4 x \)

Simplify the expression: \( (x^{1/4}y^{1/2})^{8} \)

(c) Subtract: \( 31(1-4 m+5 n) \) from \( 4 I(10 n-3 m+21) \) (d) Subtract: \( 3 a(a+b+c)-2 b(a-b+c) \) from \( 4 c(-a+b+c \)