Answer
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We have a formula for this problem.
\large{\tt{\green{Formula\implies (x+a)(x+b) = x^2+ (a+b)x+(ab)}}}Formula⟹(x+a)(x+b)=x
2
+(a+b)x+(ab)
we have been given that
x= a
a=5
b=4
So by applying the formula Above-mentioned
(a+5)(a+4)=a²+(5+4)a+(4 x 5)
\implies⟹ \large\bold{\boxed{a^2 + 9a + 20}}
a
2
+9a+20
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