Toán Lớp 7: `(5x^2−7x+3)−(x^2−x+1)=4x` tìm x làm dễ hiểu vào

Question

Toán Lớp 7:  (5x^2−7x+3)−(x^2−x+1)=4x tìm x làm dễ hiểu vào

bichquyenlien · Answer

Giải đáp + giải th&iacute;ch c&aacute;c bước giải:     (5x^2-7x+3)-(x^2-x+1)=4x   ->5x^2-7x+3-x^2+x-1=4x   ->4x^2-6x+2=4x   ->2x^2-3x+1=2x   ->2x^2-3x-2x+1=0   ->2x^2-5x+1=0   ->x^2-5/2 x +1/2=0   ->x^2- 2. x. 5/4 +25/16-17/16=0   ->x(x-5/4)-5/4(x-5/4)=17/16   ->(x-5/4)^2=17/16   -> ( left[  begin{array}{l}x- dfrac{5}{4}= dfrac{ sqrt{17}}{4}  x- dfrac{5}{4}= dfrac{- sqrt{17}}{4} end{array}  right. )    -> ( left[  begin{array}{l}x= dfrac{ sqrt{17}+5}{4}  x= dfrac{- sqrt{17}+5}{4} end{array}  right. )    Vậy x= frac{ sqrt{17}+5}{4}; frac{- sqrt{17}+5}{4}

hoquyly · Answer

Lời giải và giải thích chi tiết:     (5x^2-7x+3)-(x^2-x+1)=4x   &harr;️5x^2-7x+3-x^2+x-1=4x   &harr;️5x^2-7x+3-x^2+x-1-4x=0   &harr;️(5x^2-x^2)-(7x-x+4x)+(3-1)=0   &harr;️4x^2-10x+2=0   &harr;️x^2-5/2 x +1/2=0   &harr;️x^2-5/4x - 5/4x  + 25/16 -17/16=0   &harr;️x(x-5/4)-5/4(x-5/4)-17/16=0   &harr;️(x-5/4)^2=17/16   &harr;️|x-5/4|= sqrt{17}/4   TH1: x-5/4= sqrt{17}/4   &harr;️x= sqrt{17}/4+5/4   &harr;️x=( sqrt{17}+5)/4   TH2: x-5/4=- sqrt{17}/4   &harr;️x=- sqrt{17}/4+5/4   &harr;️x=-( sqrt{17}+5)/4