f=ax2+bx+cf = ax^2 + bx + cf=ax2+bx+c f′=2ax+bf' = 2ax + bf′=2ax+b f(2)=6f(2) = 6f(2)=6 f′(0)=2f'(0) = 2f′(0)=2 f′(1)=4f'(1) = 4f′(1)=4 から 4a+2b+c=64a + 2b + c = 64a+2b+c=6 ① b=2b = 2b=2 ② 2a+b=42a + b = 42a+b=4 ③ ②を③に代入して 2a+2=42a + 2 = 42a+2=4 a=1a = 1a=1 ④ ②、④を①に代入して 4+4+c=64 + 4 + c = 64+4+c=6 c=−2c = -2c=−2 これから a=1a = 1a=1 b=2b = 2b=2 c=−2c = -2c=−2