tính B=\(\left(x^{2007}+3x^{2006}-1\right)^{2007}\) tại x =-3
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Ta có:B=\(\left(x^{2007}+3x^{2006}-1\right)^{2007}\)
\(\Rightarrow\)B=\(\left(\left(-3\right)^{2007}+3\times\left(-3\right)^{2006}-1\right)^{2007}\)
B=\(\left(\left(-3\right)\times\left(-3\right)^{2006}+3\times\left(-3\right)^{2006}-1\right)^{2007}\)
B=\(\left(\left(\left(-3\right)+3\right)\times\left(-3\right)^{2006}-1\right)^{2007}\)
B=\(\left(0\times\left(-3\right)^{2006}-1\right)^{2007}\)
B=\(\left(0-1\right)^{2007}\)
B=\(\left(-1\right)^{2007}\)
B=\(\left(-1\right)\)
Tại x= - 3
=> \(B=\left[\left(-3\right)^{2017}+3\left(-3\right)^{2016}-1\right]^{2017}\)
=> \(B=\left[\left(-3\right)^{2017}+3^{2017}-1\right]^{2017}\)
=> \(B=\left(-1\right)^{2017}\)
=> B = - 1
Ta có:
\(B=\left(x^{2007}+3x^{2006}-1\right)^{2007}\)
\(B=\left(\left(-3\right)^{2007}+3\left(-3\right)^{2006}-1\right)^{2007}\)
\(B=\left(\left(-3\right)^{2007}+3\left(3\right)^{2006}-1\right)^{2007}\)
\(B=\left(\left(-3\right)^{2007}+3^1\left(3\right)^{2006}-1\right)^{2007}\)
\(B=\left(\left(-3\right)^{2007}+3^{1+2006}-1\right)^{2007}\)
\(B=\left(\left(-3\right)^{2007}+3^{2007}-1\right)^{2007}\)
\(B=\left(0-1\right)^{2007}\)
\(B=\left(-1\right)^{2007}\)
\(B=1\)
a) \(A=x^{15}+3x^{14}+5\)
\(=x^{14}\left(x+3\right)+5\)
\(=x^{14}.0+5\)
= 5
b) x = -3 => x + 3 = 0
\(B=\left(x^{2007}+3x^{2006}+1\right)^{2007}\)
\(=\left[x^{2006}\left(x+3\right)+1\right]^{2007}\)
\(=\left(x^{2006}.0+1\right)^{2007}\)
\(=1^{2007}=1\)
\(A=x^{15}+3.x^{14}+5\text{ biết x+3=0}\)
\(A=x^{14}.\left(x+3\right)+5\)
\(\text{Do x+3=0}\Rightarrow A=x^{14}.0+5\)
\(A=0+5\)
\(A=5\) \(\text{Vậy }A=5\text{ với x+3=0}\)
\(B=\left(x^{2007}+3.x^{2006}+1\right)^{2007}\text{ biết x=-3}\)
\(B=\left[x^{2006}.\left(x+3\right)+1\right]^{2007}\)
\(\text{Do x=-3}\Rightarrow B=\left[x^{2006}.\left(-3+3\right)+1\right]^{2007}\)
\(B=\left(x^{2006}.0+1\right)^{2007}\)
\(B=\left(0+1\right)^{2007}\)
\(B=1^{2007}\)
\(B=1\) \(\text{Vậy }B=1\text{ với x=-3}\)
Khi x=-3 thì biểu thức:
\(\Rightarrow B=\left(-3^{2007}+3.\left(-3\right)^{2006}-1\right)^{2007}\)
\(\Rightarrow B=.............\)
máy tính tính cũng không ra nha bạn
Thay \(x=-3\) vào biểu thức B ta được :
\(B=\left(-3^{2007}+3.\left(-3\right)^{2006}-1\right)^{2007}\)
\(=\left(-3^{2007}+3^{2007}-1\right)^{2007}\)
\(=-1^{2007}\)
\(=-1\)
Đặt x -2006 = y
pt <=> \(\frac{y^2-y\left(y-1\right)+\left(y-1\right)^2}{y^2+y\left(y-1\right)+\left(y-1\right)^2}=\frac{19}{49}\)
<=> \(\frac{y^2-y^2+y+y^2-2y+1}{y^2+y^2-y+y^2-2y+1}=\frac{19}{49}\)
<=> \(\frac{y^2-y+1}{3y^2-3y+1}=\frac{19}{49}\)
<=> \(49y^2-49y+49=57y^2-57y+19\)
<=> \(8y^2-8y-30=0\)
<=> \(4y^2-4y+15=0\)
Giải tiếp nha
Ta có nhận xét : \(a+b=1\) thì
\(f\left(a\right)+f\left(b\right)=\frac{4^a}{4^a+2}+\frac{4^b}{4^b+2}=\frac{4^a\left(4^a+2\right)+4^b\left(4^b+2\right)}{\left(4^a+2\right)\left(4^b+2\right)}\)
\(=\frac{4^{a+b}+2.4^a+4^{a+b}+2.4^b}{4^{a+b}+2.4^a+2.4^b+4}=\frac{2.4^a+2.4^b+8}{2.4^a+2.4^b+8}=1\)
Áp dụng kết quả trên ta có :
\(S=\left[f\left(\frac{1}{2007}\right)+f\left(\frac{2006}{2007}\right)\right]+\left[f\left(\frac{2}{2007}\right)+f\left(\frac{2005}{2007}\right)\right]+...+\left[f\left(\frac{1003}{2007}\right)+f\left(\frac{1004}{2007}\right)\right]\)
Vâyu \(S=1+1+1+...+1=1003\) (có 1003 số hạng)
\(\frac{1}{2007}.\left(\frac{1001}{2006}-2007\right)-\left(\frac{1}{2006}-2007\right).\frac{1001}{2007}\)
\(=\left(\frac{1001}{2007.2006}-\frac{2007}{2007}\right)-\left(\frac{1001}{2006.2007}-\frac{2007.1001}{2007}\right)\)
\(=\frac{1001}{2007.2006}-\frac{1001}{2006.2007}-1+1001\)
\(=-1+1001\)
\(=1000\)
B=\(\left(x^{2007}+3x^{2006}-1\right)^{2007}\)
\(B=\left[\left(-3^{2007}\right)+3\left(-3^{2006}\right)-1\right]^{2007}\)
\(B=\left[\left(-3^{2007}\right)+3.3^{2006}-1\right]^{2007}\)
\(B=\left[\left(-3^{2007}\right)+3^{2007}-1\right]^{2007}\)
\(B=\left(-1\right)^{2007}=\left(-1\right)\)
Ta có: \(B=\left(x^{2007}+3x^{2006}-1\right)^{2007}\)
Thay x = -3 vào B ta có:
\(B=\left(\left(-3\right)^{2007}+3\left(-3\right)^{2006}-1\right)^{2007}\)
=>\(B=\left(\left(-3\right)^{2007}+3\cdot3^{2006}-1\right)^{2007}\)
=>\(B=\left(\left(-3\right)^{2007}+3^{2007}-1\right)^{2007}\)
=>\(B=\left(0-1\right)^{2007}\)
\(=>B=\left(-1\right)^{2007}=-1\)