Question

use the identity (x+a)(x+b)=x2+(a+b)x+ab to find product (x+4)(x+5).​

Answer 1

ATQ,

$a = 4$

$b = 5$

Identity :

$x ^{2} + (a + b)x + ab$

$\huge\fbox\orange{Answer}$

$(x + 4)(x + 5)$

$x ^{2} + (4 + 5)x + 4 \times 5$

$x ^{2} + 9x + 20$

So, the answer is

$x ^{2} + 9x + 20$