Question icon
Grade 11Algebra

if x be the real number such that x3+4x=8,then value of the expression x7+64x2 is......

Profile image of rahul
11 Years agoGrade 11
Answers icon

1 Answer

Profile image of SHAIK AASIF AHAMED
ApprovedApproved Tutor Answer11 Years ago
Hello student,
For any integer n\geq 0,the given equation impliesxn+3=-4xn+1+8xn
so we can write such power of x in terms of lower powers.
carrying out this process iteratively gives
x7=-4x5+8x4
=8x4+16x3-32x2
=16x3-64x2+64x
=-64x2+128
so x7+64x2=128
Hence the answer is 128