(160-20p)*p=300
160p - 20p^2 - 300=0
-p^2+80p-150=0
D=6400-6000=400
p1=30
p2=50
Ответ: р=50
140(R + 0,3) = 145R
140R + 42 = 145R
5R = 42
R = 8,4
3x²+2x-1 = 3х²+3х-х-1 = 3х(х+1)-(х+1) = (х+1)(3х-1)
можно через дискриминант:
D = 4+12 = 16
x₁ = -2+4 / 6 = 1/3
x₂ = -2-4 / 6 = -1
3x²+2x-1 = 3(x - 1/3)(x+1) = (3x-1)(x+1)