Saturday

December 20, 2014

December 20, 2014

Posted by **njovu** on Tuesday, March 13, 2012 at 7:40am.

(i)alpha^3beta^3

(ii)(alpha-beta)^2

- maths -
**Reiny**, Tuesday, March 13, 2012 at 8:33amUsing the sum and product of roots property, we know

a+b = - (-4/2) = 2 and ab = 5/2, where a and b are alpha and beta

we know that

(a+b)^3 = a^3 + b^3 + 3a^2b + 3ab^2

(a+b)^3 = a^3 + b^3 + 3ab(b+a)

2^3 = a^3 + b^3 + 3(5/2)(2)

8 = a^3 + b^3 + 15

a^3 + b^3 = -7

in the same way....

(a-b)^2 = a^2 - 2ab + b^2

= a^2 +b^2 - 2ab

but a^2 + b^2 = (a+b)^2 - 2ab

so

(a=b)^2 = (a+b)^2 - 2ab - 2ab

= 4 - 5/2 - 5/2

= -1

- silly typo - maths -
**Reiny**, Tuesday, March 13, 2012 at 10:20amin the third last line I should have had

(a-b)^2 = (a+b)^2 - 2ab - 2ab

**Answer this Question**

**Related Questions**

maths - if alpha and beta are the zeros of the polynomial 2x^2-4x+5 then find ...

Math ( Polynomial ) - This time three questions - 1. If (x^2 - 1 ) is a factor ...

Math ( Polynomial ) - This time three questions - 1. If (x^2 - 1 ) is a factor ...

Math - If alpha and beta are the zeros of the polynomial ax^2 + bx + c then ...

trig - evaluate the following in exact form, where the angeles alpha and beta ...

maths - If alpha beta are the roots of a^2 +bx + c = 0. find the values of (beta...

maths - If alpha and beta are the zeros of the polynomial p(x)=x^2+x+1 then find...

Math - Given that sin alpha=4/sqrt65, pi/2<alpha<pi, and cos beta=-3/...

physics - Two radar stations A and B, are separated by horizontal distance of (...

Math - how i solve this two equations ib order to find alpha and beta 2=cos(...