Step-by-step explanation:
By replacing x with 4, we get
[tex]\\ \sf\bull\longmapsto h(x)=\dfrac{1}{4}x^4-3x^3[/tex]
[tex]\\ \sf\bull\longmapsto h(4)[/tex]
[tex]\\ \sf\bull\longmapsto \dfrac{1}{4}4^4-3(4)^3[/tex]
[tex]\\ \sf\bull\longmapsto 4^3-3(64)[/tex]
[tex]\\ \sf\bull\longmapsto 64-192[/tex]
[tex]\\ \sf\bull\longmapsto -128[/tex]