if 3x3+ 4x2+ 7x + 9=3479, and "x" is a positive real number, what is the value of x3+ 5x2+ 7?
Write the explanation? Answer in proper steps urgently
Answer :
We have : 3x3 + 4x2 + 7x + 9 = 3479
So we can write it As :
3x3 + 4x2 + 7x + 9 - 3479 = 0
3x3 + 4x2 + 7x - 3470 = 0
3x3 + 34x2 - 30x2 + 347x - 340x - 3470 = 0
3x3 + 34x2 + 347x - 30x2 - 340x - 3470 = 0
x ( 3x2 + 34x+ 347 ) - 10 ( 3x2 + 34x+ 347 ) = 0
( x - 10 ) ( 3x2 + 34x+ 347 ) = 0
So,
x = 10 , that is a positive real number , So
And
For 3x2 + 34x+ 347 , we check
b2 - 4ac = 342 - 4 3 347 = 1156 - 4164 = -3008 , So
3x2 + 34x+ 347 Does not give any real value of x
So,
x = 10 put in
x3 + 5x2 + 7 = 103 + 5 ( 10 )2 + 7 = 1000 + 500 + 7 = 1507 ( Ans )
We have : 3x3 + 4x2 + 7x + 9 = 3479
So we can write it As :
3x3 + 4x2 + 7x + 9 - 3479 = 0
3x3 + 4x2 + 7x - 3470 = 0
3x3 + 34x2 - 30x2 + 347x - 340x - 3470 = 0
3x3 + 34x2 + 347x - 30x2 - 340x - 3470 = 0
x ( 3x2 + 34x+ 347 ) - 10 ( 3x2 + 34x+ 347 ) = 0
( x - 10 ) ( 3x2 + 34x+ 347 ) = 0
So,
x = 10 , that is a positive real number , So
And
For 3x2 + 34x+ 347 , we check
b2 - 4ac = 342 - 4 3 347 = 1156 - 4164 = -3008 , So
3x2 + 34x+ 347 Does not give any real value of x
So,
x = 10 put in
x3 + 5x2 + 7 = 103 + 5 ( 10 )2 + 7 = 1000 + 500 + 7 = 1507 ( Ans )