Question

find the value of a.....??

Answer 1

Hey

Here is your answer,

X-4 is a factor.
Therefore ,
X-4=0
X=4

Substitute the value of x in equation,

5x^3 -7x^2 -9x -28 =0
5(4)^3 -7(4)^2 -a(4) -28=0
5x64 -7x16 -4a -28=0
320 - 112 - 28 -4a=0
460 - 4a=0
4a=460
a=460/4
= 115.

Hope it helps you!