Question

factorise: 2x cube - 5x square + 9x - 8 ​

Answer 1

p(x) = 2x square - 5x square + 9x - 8

We have,

x-3 = 0

x = 3

Hence,

p(3) = 2 (3X3) + 5 (3X3) + 9 (3X3) -8

= 2 X 9 + 5 X 9 + 9 X 9 - 8

= 18 + 45 + 81 - 8

= 136

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Answer 2

Step-by-step explanation:

Given polynomial is of 3 rd degree so

We Wii have 3 factors

let f(x) = 2x^3 -5x^2–19x +42

Try x= +— 1 or x=+ -2

By remainder theorem if remainder of polynomial is 0 for that particular value x=a then we can say that (x--a ) is a FACTOR of f(x)

Put x=2 in f(x)

f(2) = 16--20-38+42 =0

(x-2) is afactor of f(x)

Dividing f(x) by (x-2) long method or synthetic method we get

(2x^2-x--21)

Factors of f(x) given are

(x-2) ( 2x^2-x--21)

Factors of

2x^2---x-21 =

= 2x^2 --7x+6x-21

=x(2x--7) +3(2x--7)

= (x+3)(2x--7)

So the factors of the given polynomial are

( x-2) (x+3) (2x-7)