Use suitable identities to find the products : $(3 x+4)(3 x-5)$
Use suitable identities to find the products : $(3 x+4)(3 x-5)$
$(3 x+4)(3 x-5)$ :
Using the identity $(x+a)(x+b)=x^{2}+(a+b) x+a b,$ we have
$(3 x+4)(3 x-5) =(3 x)^{2}+[4+(-5)] 3 x+[4 \times(-5)] $
$=9 x^{2}+[-1] 3 x+[-20]=9 x^{2}-3 x-20$
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