Question

factorise 5a^2-18a-8
$5a {}^{2} - 18a - 8$
​

Answer 1

Answer:

( a-4 ) ( 5a + 2 )

Step-by-step explanation:

Given---> 5a² - 18a - 8

To find ---> Factors of given expression

Solution--->

5a² - 18a - 8

We do factors by method of splitting the middle terms . For this first we multiply coefficient of a² and constant term .

Coefficient of a² = 5

Constant term = 8

By multiplying coefficient of a² and constant term we get 8 × 5 = 40

Now we do prime factorization of 40 and get two numbers whose difference is 18 .

Required numbers are 20 and 2

20 × 2 = 40

20 - 2 = 18

Now,

5a² - 18a - 8

Putting 18 = 20 - 2 in it , we get

= 5 a² - ( 20 - 2 ) a - 8

= 5a² - ( 20a - 2a ) - 8

= 5a² - 20a + 2a - 8

= 5a ( a - 4 ) + 2 ( a - 4 )

= ( a - 4 ) ( 5a + 2 )