2. \( \mathrm{f}(x)=x^{2}-4 \) \( \mathrm{~g}(x)=2 x+1 \) Solve \( \quad \mathrm{fg}(x)>0 \) Show clear algebraic working.

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

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

19 days of March 2015 . \( \begin{array}{llll}\text { (1) } ₹ 1530 & \text { (2) } ₹ 1260 & \text { (3) } ₹ 1620 & \text { (4) } ₹ 1710\end{array} \) \( x \propto \frac{1}{y} \). When \( y=6, x=14 \). What is the constant of variation ? \( \begin{array}{llll}\text { (1) } 94 & \text { (2) } 84 & \text { (3) } 82 & \text { (4) } 72\end{array} \) If \( x \) varies directly as \( y \), which number will replace the question

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

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