Toán Lớp 7: tìm nghiệm i) – x^4-2016 k) 3(x + 1) – 5x(x + 1) l) 2(x – 3) – 4(5 – 2x) – 3x

Question

Toán Lớp 7:  tìm nghiệm i) – x^4-2016 k) 3(x + 1) – 5x(x + 1) l) 2(x – 3) – 4(5 – 2x) – 3x

thucquyenlan · Answer

$ text{i) -x ⁴-2016=0}$     $ text{&hArr;x⁴+2016= 0}$     $ text{M&agrave; v&igrave; x⁴&ge;0 n&ecirc;n x⁴+2016&ge;2016>0}$     $ text{N&ecirc;n phương tr&igrave;nh v&ocirc; nghiệm}$     $ text{k) 3(x+1)-5x.(x+1)=9}$     $ text{&hArr;3x+3-5.x&sup2;-5x=0}$     $ text{&hArr;-5.x&sup2;-2x+3=0}$     $ text{&hArr;5.x&sup2;+2x-3=0}$     $ text{&hArr;5.x&sup2;+5x-3x-3=0}$     $ text{&hArr;5x(x+1)-3(x+1)=0}$     $ text{&hArr;(5x-3).(x+1)=0}$     $ text{&rArr; ( left[  begin{array}{l}x= frac{5}{3}  x=-1 end{array}  right. )}$     $ text{l) 2.(x-3)-4.(5-2x)-3x=0}$     $ text{&hArr;2x-6-20+8x-3x}$     $ text{&hArr;7x=26}$     $ text{&hArr;x=$ frac{26}{7}$  }$

ngocle44 · Answer

Giải đáp + Lời giải và giải thích chi tiết:     i)   -x^4-2016=0    to -x^4 = 2016    to x^4 =-2016 (v&ocirc; l&yacute;)   Vậy x  in  emptyset   k)   3(x+1)-5x(x+1) = 0    to 3x + 3 - 5x^2 - 5x = 0    to -5x^2 - 2x + 3 = 0    to -(5x^2+2x-3) = 0    to -(5x^2-3x+5x-3) = 0    to -[x(5x-3)+(5x-3)] = 0    to -(x+1)(5x-3) = 0   TH1 : x + 1 = 0  to x = -1   TH2 : 5x - 3 = 0  to 5x = 3  to x = 3/5   Vậy S = {-1,3/5}   l)   2(x-3)-4(5-2x)-3x=0    to 2x - 6 - 20 + 8x - 3x = 0    to 7x - 26 = 0    to 7x = 26    to x = 26/7   Vậy S = {26/7}