Question

900u* (70-u)=0плиз помогите срочно

Answer 1

63000u-900u^2=0
U(63000-900u)=0
U=0или 63000-900u=0
-900u=-63000
U=70

Answer 2

63000u-900u^2=0
-900u^2+63000u=0  | : - 900
u^2-70u=0
u(u-70)=0
u1=0
u2=70