a.
`y=-13x^2+13x-2020`
`\to y'=(-13x^2)'+(13x)'-(2020)'`
`\to y'=-26x+13`
b.
`f(x)=\frac{x^2-13}{x+13}`
`\to f'(x)=\frac{(x^2-13)'(x+13)-(x^2-13)(x+13)'}{(x+13)^2}`
`\to f'(x)=\frac{2x.(x+13)-(x^2-13).1}{(x+13)^2}`
`\to f'(x)=\frac{2x^2+26x-x^2+13}{(x+13)^2}`
`\to f'(x)=\frac{x^2+26x+13}{(x+13)^2}`
c.
`f(x)=13x^2(x^2-13)=13x^4-169x^2`
`\to f'(x)=(13x^4)'-(169x^2)'`
`\to f'(x)=52x^3-338x`
