math
posted by Sara
A polynomial function function is defined by the equation p(x)=3x3+ax2+bx+7, where a, bE/. If p(2)=5 and p(1)=14 then the value of a+b is...

Reiny
From p(2)=5 and p(1)=14
we have two points (2,5) and (1,14)
so,
3(8) + a(4) 2b + 7 = 5
4a  2b = 22 > 2a  b = 11
3(1) + a(1) + b(1) + 7 = 14 > a + b = 4
adding:
3a = 15
a = 5, then b = 1
a+b = 51 = 4
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