Найти Х (7-x)(x+5)-x(4-x)=14

Question

Найти Х (7-x)(x+5)-x(4-x)=14

Answer 1

(7-х)(х+5)-х(4-х)=14

7х+35-х(квадрат)+5х-4х+х(квадрат)=14

7х+5х-4х+35=14

8х=14-35

8х=-21

х=-21:8

х=-2.625

Answer 2

X*(7X + 35 - X^2 - 5X) - 4X + X^2 = 14

7X^2 + 35X - X^3 - 5X^2 - 4X + X^2 = 14

- X^3 + 3X^2 + 31X - 14 = 0

F ' = -3X^2 + 6X + 31

...................

-3X^2 + 6X + 31 = 0

D = 36 - 4*(-3)*31 = 36 - 4*(-93) = 36+372=408  V D = 20.1

X1 = - 6 + 20.1 \ - 6 =  - 2.35

X2 = - 6 - 20.1 \ -6 = + 4.35