Question

Using identity ( x+ a )(x + b) = x2 + ( a + b )x + ab. Find
( 3x + 5 ) ( 3x – 1 )​

Answer 1

Solution :-

Given that, we have to Solve (3x+5)(3x-1) by using algebraic identites (x+a)(x+b)

so, let suppose that, x = 3x , a = 5 and b = -1

Now, we can solve it by putting this value in (x+a) (x+b) = x² + (a+b)x +ab

let's do it ====>

(x+a) (x+b) = x² + (a+b)x +ab

=> (3x +5) ( 3x-1) = (3x)² + ( 5-1)3x + 5×-1

=> ( 3x +5)(3x-1) = (3x)² + 4×3x + -5

=> ( 3x +5)(3x-1) = 9x² + 12x -5

hence your answer is -

( 3x +5)(3x-1) = 9x² + 12x -5