Math, asked by sk700, 1 year ago

factorise 15x^2-x-28

Answers

Answered by Anonymous
71
15x2-x-28=0 

Two solutions were found :

 x = -4/3 = -1.333
 x = 7/5 = 1.400

Step by step solution :

Step  1  :

Equation at the end of step  1  :

((3•5x2) - x) - 28 = 0

Step  2  :

Trying to factor by splitting the middle term

 2.1     Factoring  15x2-x-28 

The first term is,  15x2  its coefficient is  15 .
The middle term is,  -x  its coefficient is  -1 .
The last term, "the constant", is  -28 

Step-1 : Multiply the coefficient of the first term by the constant  15 • -28 = -420 

Step-2 : Find two factors of  -420  whose sum equals the coefficient of the middle term, which is   -1 .
Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above,  -21  and  20 
                     15x2 - 21x + 20x - 28

Step-4 : Add up the first 2 terms, pulling out like factors :
                    3x • (5x-7)
              Add up the last 2 terms, pulling out common factors :
                    4 • (5x-7)
Step-5 : Add up the four terms of step 4 :
                    (3x+4)  •  (5x-7)
             Which is the desired factorization

Equation at the end of step  2  :

(5x - 7) • (3x + 4) = 0

Answered by Anonymous
321
given us that

15x² - x - 28

= 15x² - ( 21 - 20 )x - 28

= 15x² - 21x + 20x - 28

= 3x ( 5x - 7 ) + 4 ( 5x - 7 )

= ( 3x + 4 ) ( 5x - 7 )

- Answered by a Useless user
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