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I count on in equal steps,
My fourth number is 39, my fifth number is 43.
2
39
43
What is my first number?

Anyone know?


Sagot :

  • a_5=43
  • a_3=39

common difference=d=43-39=4

We need first term a

[tex]\\ \sf{:}\dashrightarrow a_5=43[/tex]

[tex]\\ \sf{:}\dashrightarrow a+4d=43[/tex]

[tex]\\ \sf{:}\dashrightarrow a+4(4)=43[/tex]

[tex]\\ \sf{:}\dashrightarrow a+16=43[/tex]

[tex]\\ \sf{:}\dashrightarrow a=27[/tex]