Let p(x) be a polynomial of° 4 having extremum at x = 1, 2 and lim_(x → 0)(1 + p(x)/x²) = 2. Then the value of p(2) is
p(x) degree 4, extrema at x=1, 2
limx→0(1+x2p(x))=2
To find: p(2)
use: limit condition, then p′(1)=p′(2)=0
p(x)=ax4+bx3+cx2+dx+e
limx→0(1+x2p(x))=2⇒x2p(x)→1
x2p(x)=ax2+bx+c+xd+x2e→1
⇒d=e=0,c=1
p(x)=ax4+bx3+x2
1. p′(1)=p′(2)=0
2. solve for a,b
3. p(2)
p′(x)=4ax3+3bx2+2x
p′(1)=0: 4a+3b+2=0
p′(2)=0: 8a+3b+1=0
4a=1⇒a=41
3b=−3⇒b=−1
p(x)=41x4−x3+x2
p′(x)=x3−3x2+2x=x(x−1)(x−2)
p(2)=41(16)−8+4=4−8+4=0
p(2)=0