Держи под буквой(а), со вторым непонятки
Вот тебе решение..........................
100-21=79% cухого вещества
100-60=40%
0,79*20=0,4х
х=0,79*20/0,4=39,5
ответ надо взять 39,5 кг
![\sqrt{x+3} * \sqrt{4x+5} \ \textless \ 6](https://tex.z-dn.net/?f=+%5Csqrt%7Bx%2B3%7D+%2A+%5Csqrt%7B4x%2B5%7D+%5C+%5Ctextless+%5C+6)
; _________________________
![\sqrt{(x+3)(4x+5)} \ \textless \ \sqrt{36}](https://tex.z-dn.net/?f=+%5Csqrt%7B%28x%2B3%29%284x%2B5%29%7D+%5C+%5Ctextless+%5C++%5Csqrt%7B36%7D+)
; _______________________
![(x+3)(4x+5) \ \textless \ 36](https://tex.z-dn.net/?f=+%28x%2B3%29%284x%2B5%29+%5C+%5Ctextless+%5C++36)
; ________________________________
![4x^2+5x+12x+15-36\ \textless \ 0](https://tex.z-dn.net/?f=4x%5E2%2B5x%2B12x%2B15-36%5C+%5Ctextless+%5C+0)
; ____________________________
![4x^2+17x-21\ \textless \ 0](https://tex.z-dn.net/?f=4x%5E2%2B17x-21%5C+%5Ctextless+%5C+0)
; _________________________________
![4x^2+17x-21=0; D=17^2-4*4*(-21)=289+336=625=25^2](https://tex.z-dn.net/?f=4x%5E2%2B17x-21%3D0%3B+D%3D17%5E2-4%2A4%2A%28-21%29%3D289%2B336%3D625%3D25%5E2)
; ____________
![x_1= \frac{-17-25}{2*4} =-5,25; x_2= \frac{-17+25}{2*4} =1](https://tex.z-dn.net/?f=x_1%3D+%5Cfrac%7B-17-25%7D%7B2%2A4%7D+%3D-5%2C25%3B+x_2%3D+%5Cfrac%7B-17%2B25%7D%7B2%2A4%7D+%3D1)
; ___________
_______ + ____________________ - ____________________ + ________
-----------------------------(-5,25)----------------------------------------(1)---------------------------------
x∈(-5,25;1)