WAEC Further Mathematics 2019 Paper

Concept:Solve the radical equation by isolating the square root, then squaring both sides and solving for positive $x$.Explanation:Given: $6\sqrt{4x^2+1}=13x$, where $x>0$.Divide both sides by $6$:$\sqrt{4x^2+1}=\dfrac{13x}{6}$.Square both sides to eliminate the square root:$4x^2+1=\dfrac{169x^2}{36}$.Multiply both sides by $36$:$144x^2+36=169x^2$.Rearrange the equation:$169x^2-144x^2=36$.Simplify:$25x^2=36$.Divide both sides by $25$:$x^2=\dfrac{36}{25}$.Since $x>0$, take the positive square root:$x=\dfrac{6}{5}$.Answer:$x=\dfrac{6}{5}$, which is option A.