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here are the first five terms of a quadratic sequence (1 8, 21, 40, 65). the nth term of this sequence can be written in the form (an2 + bn). where a and b are integers. work out the value of a and the value of b

Respuesta :

lublana

Answer:

a=3 and b=-2

Step-by-step explanation:

We are given that five  terms of a quadratic sequence are

1 8, 21, 40, 65.

The nth term of this sequence

=[tex]an^2+bn[/tex]

We have to find the value of a and b where a and b are integers.

For n=1

[tex]a+b=1[/tex]   ......(1)

For n=2

[tex](2)^2a+2b=8[/tex]

[tex]4a+2b=8[/tex]

[tex]2a+b=4[/tex]   .....(2)

Subtract equation (1) from (2) we get

[tex]2a-a=4-1=3[/tex]

[tex]a=3[/tex]

Using the value of a=3 in equation (1)

[tex]3+b=1[/tex]

[tex]b=1-3=-2[/tex]

Hence, the value of

a=3 and b=-2