tolong banyu ya.............

[tex]\displaystyle f(x)=20x^{\frac72}+2x^{\frac52}+10x\\\\f'(x)=20\cdot\frac72x^{\frac72-1}+2\cdot\frac52x^{\frac52-1}+10\\f'(x)=70x^{\frac52}+5x^{\frac32}+10\\\\f''(x)=70\cdot\frac52x^{\frac52-1}+5\cdot\frac32x^{\frac32-1}\\f''(x)=175x^{\frac32}+\frac{15}2x^{\frac12}\\f''(4)=175(4)^{\frac32}+\frac{15}2(4)^{\frac12}\\f''(4)=175(8)+\frac{15}2(2)\\f''(4)=1400+15\\\boxed{\boxed{f''(4)=1415}}[/tex]

f (4) = 20 × (2) ^2 × ^ 7/2 + 2 × (2) ^2 × 5/2 + 10 × 4

= 20 × (2) ^7 + 2 × (2)^5 + 40

= 20×128 + 2×32 + 40

= 2560+64+40

=2664