Toán Lớp 8: Bài 1: Rút gọn các biểu thức: a/ 3x( x – 2 ) – 5x(1 – x ) – 8( x2 – 3 ) b/ ( x + 5 )2 – ( x + 3 ) ( x – 3 ) c/ x( x – 5 ) ( x + 5 ) – (

Question

Toán Lớp 8:  Bài 1: Rút gọn các biểu thức: a/ 3x( x – 2 ) – 5x(1 – x ) – 8( x2 – 3 ) b/ ( x + 5 )2 – ( x + 3 ) ( x – 3 ) c/ x( x – 5 ) ( x + 5 ) – ( x + 2 ) ( x2 – 2x + 4 ) d/ x( x2 + x + 1 ) – x2( x + 1 ) – x + 5 Bài 2: Tìm giá trị của x, Biết :  x^2 + x( x + 4 ) = 0

dantam45 · Answer

Giải đáp+Lời giải và giải thích chi tiết:     B&agrave;i 1:     a) 3x.(x-2)-5x.(1-x)-8.(x&sup2;-3)     = 3x&sup2;-6x-5x+5x&sup2;-8x&sup2;+24     = (3x&sup2;+5x&sup2;-8x&sup2;)-(6x+5x)+24     = -11x+24     b) (x+5)&sup2;-(x+3).(x-3)     = (x&sup2;+2.x.5+5&sup2;)-(x&sup2;-9)     = x&sup2;+10x+25-x&sup2;+9     = (x&sup2;-x&sup2;)+10x+(25+9)     = 10x+34     c) x.(x-5).(x+5)-(x+2).(x&sup2;-2x+4)     = x.(x&sup2;-25)-(x&sup3;+2&sup3;)     = x&sup3;-25x-x&sup3;-8     = (x&sup3;-x&sup3;)-25x-8     = -25x-8     d) x.(x&sup2;+x+1)-x&sup2;.(x+1)-x+5     = x&sup3;+x&sup2;+x-x&sup3;-x&sup2;-x+5     = (x&sup3;-x&sup3;)+(x&sup2;-x&sup2;)+(x-x)+5     = 5     B&agrave;i 2:     x&sup2;+x.(x+4)=0     &harr; x&sup2;+x&sup2;+4x=0     &harr; 2x&sup2;+4x=0     &harr; x.(2x+4)=0     &harr; x=0          &harr; x=0      &harr; x=0     &harr; 2x+4=0    &harr; 2x=-4  &harr; x=-2     Vậy x &isin; {0;-2}     $anhnguyenff        ✨ *ALL STARS*✨