Question

2. Quem é o a1 da PA dado a12 = 5 e r = - 4?
A)48
B)49
C)50
D)52
E)60

Answer 1

$\mathsf{a_{12}=a_{1}+11r}\\\mathsf{5=a_{1}+11.(-4)}\\\mathsf{a_{1}-44=5}\\\mathsf{a_{1}=5+44}$

$\huge\boxed{\boxed{\boxed{\mathsf{a_{1}=49\checkmark}}}}$

$\huge\boxed{\boxed{\boxed{\mathsf{\maltese~~alternativa~b}}}}$