need ur help people on few questions

Q1>>>Show that the roots of the equation

(x – a) (x – b) + (x – b) (x – c) + (x – c) (x – a) = 0

are always real and they cannot be equal unless a = b = c

Q2>>If w is a complex cube root of unity, then show that

(1 + 5w2 + w4) (1 + 5w + w2) (5 + w + w2) =64

Q3>>>A question paper contains 12 questions divided into two sections. Section I contains

7 questions and section II contains 5 questions. In how many ways can a candidate

choose the questions if he has to select 8 questions in all with teh restriction of

atleast 3 questions from each section?

Q4>>Let A =

|1 -1 0 |

|2 2 4 |

|2 3 4 |

and B =

|4 2 4 |

|0 1 2 |

|2 1 5 |

Find AB.

Use this to solve the following system of equations:

x – y = 3

2x + 3y + 4z = 17

y + 2z = 7

thanku for ur help frndz