Toán Lớp 8: Thu gọn biểu thức:
C/ x+1/x-2+4/x+2+2-7x/x^2-4
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 8: Thu gọn biểu thức:
C/ x+1/x-2+4/x+2+2-7x/x^2-4
Comments ( 1 )
=(x+1)/(x-2)+4/(x+2)+(2-7x)/(x²-2²)
– Áp dụng hằng đẳng thức số $3$ : A²-B²=(A-B)(A+B)
=(x+1)/(x-2)+4/(x+2)+(2-7x)/((x-2)(x+2))
MTC:(x+2)(x-2)
=>(x+1)/(x-2)=((x+1)(x+2))/((x+2)(x-2))=(x(x+2)+1(x+2))/((x+2)(x-2))=(x²+2x+x+2)/((x+2)(x-2))=(x²+3x+2)/((x+2)(x-2))
4/(x+2)=(4(x-2))/((x+2)(x-2))=(4x-8)/((x+2)(x-2))
=(x²+3x+2)/((x+2)(x-2))+(4x-8)/((x+2)(x-2))+(2-7x)/((x+2)(x-2))
=(x²+3x+2+4x-8+2-7x)/((x+2)(x-2))
=(x²+(3x+4x-7x)-(8-2-2))/((x+2)(x-2))
=(x²+0-4)/((x+2)(x-2))
=(x²-2²)/((x+2)(x-2))
=(x²-2²)/(x²-2²)
=1
Vậy (x+1)/(x-2)+4/(x+2)+(2-7x)/(x²-4)=1