Cho M(x)=ax^2+bx+c.Xac dinh a,b,c biet f(1)=0,f(-1)=2,f(2)=5 27/09/2021 Bởi Arianna Cho M(x)=ax^2+bx+c.Xac dinh a,b,c biet f(1)=0,f(-1)=2,f(2)=5
Đáp án: `f(1)=a+b+c=0` `f(-1)=a-b+c=2` `f(2)=4a+2b+c=5` Ta có : `f(1)-f(-1)=a+b+c-a+b-c=2b=-2` `=> b=-1` `f(1) => a+c=1` Thay vào `f(2) => 3a+a+2.(-1)+c=5` `=> 3a+1+(-2)=5` `=> 3a =6` `=> a=2` `=> c=1-2=-1` Vậy `(a;b;c)=(2;-1;-1)` Bình luận
f(1)=a+b+c=0 f(2)=4a+2b+c=5 f(-1)=a-b+c=2 =>f(1)-f(2)=2b=-2 =>b=-1 =>a+c=1 Thay vao f(2) =>3a-2+1=5 =>a=2 =>c=-1 Bình luận
Đáp án:
`f(1)=a+b+c=0`
`f(-1)=a-b+c=2`
`f(2)=4a+2b+c=5`
Ta có : `f(1)-f(-1)=a+b+c-a+b-c=2b=-2`
`=> b=-1`
`f(1) => a+c=1`
Thay vào `f(2) => 3a+a+2.(-1)+c=5`
`=> 3a+1+(-2)=5`
`=> 3a =6`
`=> a=2` `=> c=1-2=-1`
Vậy `(a;b;c)=(2;-1;-1)`
f(1)=a+b+c=0
f(2)=4a+2b+c=5
f(-1)=a-b+c=2
=>f(1)-f(2)=2b=-2
=>b=-1
=>a+c=1
Thay vao f(2)
=>3a-2+1=5
=>a=2
=>c=-1