\(x^{15}-\left(7+1\right)x^{14}+\left(7+1\right)x^{13}....+\left(7+1\right)x-5\)

\(=x^{15}-\left(x+1\right)x^{14}+\left(x+1\right)x^{13}....+\left(x+1\right)x-5\)

\(=x^{15}-x^{15}-x^{14}+x^{14}+x^{13}....-x^3-x^2+x^2+x-5\)

\(=x-5=7-5=2\)

ai ma biet

x = 7 => x + 1 = 8

=> Biểu thức có giá trị là:

x¹⁵ - (x+1).x¹⁴ + (x+1).x¹³ - ... + (x+1).x - 5

= x¹⁵ - x¹⁵ - x¹⁴ + x¹⁴ + x¹³ - ... + x² + x - 5

= x - 5

= 7 - 5

= 2

x=7

=>x+1=8

=> A= x^15 - 8x^14 + 8x^13 - 8x^12 +....- 8x^2 + 8x - 5 

=x¹⁵-(x+1)x¹⁴+(x+1)x¹³-(x+1)x¹²+...-(x+1)x²+(x+1)x-5

=x¹⁵-x¹⁵-x¹⁴+x¹⁴+x¹³-x¹³-x¹²+...-x³-x²+x²+x-5

=x-5

=>A=7-5=2

Vậy A=2 khi x=7

\(B=x^{15}-8x^{14}+8x^{13}-8x^{12}+...+8x-5\)

\(=x^{15}-\left(x+1\right)x^{14}+\left(x+1\right)x^{13}-\left(x+1\right)x^{12}+...+\left(x+1\right)x-x+2\)

\(=x^{15}-x^{15}-x^{14}+x^{14}+x^{13}-x^{13}-x^{12}+...+x^2+x-x+2\)

\(=2\)

Họ đã gợi ý cho rồi thì bạn còn hỏi làm gì nữa

x=7=>x+1=8

A=x¹⁵-(x+1)¹⁴+(x+1)x¹³-(x+1)x¹²+...-(x+1)x²+(x+1)x-5=x¹⁵-x¹⁵-x¹⁴+x¹⁴+x¹³-x¹³-x¹²+...-x³-x²+x²+x-5=7-5=2

8 day dung 100%

\(B=x^{15}-8x^{14}+8x^{13}-8x^{12}+...+8x-5\)

\(=x^{15}-\left(x+1\right)x^{14}+\left(x+1\right)x^{13}-\left(x+1\right)x^{12}+...+\left(x+1\right)x-x+2\)

\(=x^{15}-x^{15}-x^{14}+x^{14}+x^{13}-x^{13}-x^{12}+...+x^2+x-x+2\)

\(=2\)

=231313131313131313131221333t6543311

Ta có:

x=7=>x+1=8

A=x¹⁵-(x+1)¹⁴+(x+1)x¹³-(x+1)x¹²+...-(x+1)x²+(x+1)x-5=x¹⁵-x¹⁵-x¹⁴+x¹⁴+x¹³-x¹³-x¹²+...-x³-x²+x²+x-5=7-5=2

Vậy A=2

Ta có : x = 7 ⇒ x + 1 = 8

Thay x + 1 = 8 vào A , ta được :

A = x15 - ( x + 1)x14 + ( x + 1)x13 - ( x + 1)x12 +....- ( x + 1)x2 + ( x + 1)x - 5

A = x15 - x15 - x14 + x14 + x13 - x13 - x12 +....- x3 - x2 + x2 + x - 5

A = x - 5 = 7 - 5 = 2

\(B=x^{15}-8x^{14}+8x^{13}-8x^{12}+...+8x-5\)

\(=x^{15}-\left(x+1\right)x^{14}+\left(x+1\right)x^{13}-\left(x+1\right)x^{12}+...+\left(x+1\right)x-x+2\)

\(=x^{15}-x^{15}-x^{14}+x^{14}+x^{13}-x^{13}-x^{12}+...+x^2+x-x+2\)

\(=2\)