Question

If x + y + z = 5 & xy + yz + zx = 7, find the value of x^3 + y^3 + z^3 - 3xyz.
Plz tell fast

Answer 1

Answer:

20

Step-by-step explanation:

we know that (a+b+c)^2=a^2+b^2+c^2+2ab+2ac+2bc

bu substitution

a=x,b=y,c=z

we get

(x+y+z)^2 =x^2+y^2+z^2+2xy+2yz+2zx

(5)^2 =x^2+ y^2 + z^2 +2(xy+yz+zx)

25 = x^2+ y^2+z^2+2(7)

25= x^2+ y^2 + z^2+ 14

9 = x^2+ y^2 + z^2.............(1)

we know that

a3+ b3+c3-3ab=(a+b+c)(a2+b2+c2-ab-bc-ca)

substitute the values

x3+y3+z3-3xy=(x+y+z)(x2+y2+z2-xy-yz-zx)

x3+y3+z3-3xy=(5)(9-5)

x3+y3+z3-3xy=20

Answer 2

Answer:

20

Step-by-step explanation:

25 - 14 = 11

11 - 7 = 4

5x4 = 20