Do any one of them, please help needed​

a = -3

Step-by-step explanation:

f(x) = 5x³+4x²+3x-4a

f(-1) = 8

therefore , x = -1

substituting x = -1 in 5x³ + 4x² +3x-4a

5(-1)³ + 4(-1)² + 3(-1) - 4a. = 8

-5 + 4 -3 - 4a = 8

-8 + 4 -4a = 8

-4 - 4a = 8

shifting -4 from LHS to RHS

-4a = 8+4

-4a = 12

therefore

-a = 3

a = -3

ANS = the value of a = -3

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a28=58

step-by-step explanation:

a1=a1+(n-1)d

a28= 4+ (28-1)2

a28=4+(27)(2)

a28=4+54

a28=58