H2O wrote:
我記得有個仆街仔搞佢下面(?
f(x) = 2x^3 + ax^2 + bx + 3 ( O )SiU_LeAf wrote:
Q. f(x) = ( 2x^3 + ax^2 + bx + 3 ), f(x) / (( x - 1 ) ( x + 2 ))後, 餘式是 ( 2x + 1 ), 求 f(1) 及 f(-2).
A.
2x^3 + ax^2 + bx + 3 + 2x + 1
= 2x^3 + ax^2 + ( b + 2 )x + 4
代x=1,
0 = 2(1)^3 + a(1)^2 + ( b + 2 )(1) + 4
0 = 2 + a + b + 6
f(1) = 2(1)^3 + a(1)^2 + b(1) + 3
f(1) = 2 + a + b + 3
f(1) = - 3
f(-2)也是這樣做所以小葉不打出來了, 順便說如果小葉沒算錯的話f(-2)應該是=3的說
f(x) = p(x)(x-1)(x+2) + 2x + 1 ( O )
f(x) = 2x^3 + ax^2 + bx + 3 + 2x + 1 ( X!!!!! )
f(x) = p(x)(x-1)(x+2) + 2x + 1 = (p(x)(x+2)+2)(x-1) + 3
f(1) = 0 + 3 = 3
小葉你砍掉重練吧