Question

Gút gọn phân thứcN=\(\dfrac{x^2+3x-4}{x^2+10x+25}\)tìm giá trị của N tại x=-18

giúp mk vs ml cần gắp lắm

Answer 1

N= \(\dfrac{x^2+3x-4}{x^2+10x+25}\)

N=\(\dfrac{x^2-x+4x-4}{\left(x+5\right)^2}\)

N=\(\dfrac{x\left(x-1\right)+4\left(x-1\right)}{\left(x+5\right)^2}\)

N=\(\dfrac{\left(x-1\right)\left(x+4\right)}{\left(x+5\right)^2}\)

Thay x= -18 vào N, ta có:

N=\(\dfrac{\left[\left(-18\right)-1\right]\left[\left(-18\right)+4\right]}{\left[\left(-18\right)+5\right]^2}\)

N= \(\dfrac{266}{169}\)

Answer 2

N=\(\dfrac{x^2-1x+4x-4}{x^2+5x+5x+25}\)

\(N=\dfrac{\left(x^2-1x\right)+\left(4x-4\right)}{\left(x^2+5x\right)+\left(5x+25\right)}\)

\(N=\dfrac{x\left(x-1\right)+4\left(x-1\right)}{x\left(x+5\right)+5\left(x+5\right)}\)

\(N=\dfrac{\left(x+4\right)\left(x-1\right)}{\left(x+5\right)\left(x+5\right)}\)

\(N=\dfrac{\left(x+4\right)\left(x-1\right)}{\left(x+5\right)^2}\)

Answer 3

Thay x= -18 vào phân thức N ta được:

\(N=\dfrac{\left(-18+4\right)\left(-18-1\right)}{\left(-18+5\right)^2}\)

\(N=\dfrac{-14.-19}{\left(-13\right)^2}\)

\(N=\dfrac{266}{169}\)