T=7x^3-4 t=7×3x^2
f=t^5/21dt
1/21×ft^5dt
1/21×t^6/6
1/21×(7x^3-4)^6/6
(7x^3-4)^6/126
2). 3×fx^3dx/(x^4+1)^2
t=x^4+1
3×f1dt/4t^2
3×1/4×f1dt/t^2
3/4×(-1/x^4+1)
-3/4x^4+4
3). f6x^2-8x-5dx
2x^3-2x^4-5x
2x^3-2x^4-5x |^5 ,2
2×5^3-2×5^4-5×5-(2×2^3-2×2^4-5×2)
-999
/ это дробь