Toán Lớp 8: a) x^2+5x-6=0 b) x^2-5x+6=0 c) x^2-3x-18=0 d) x^2-13x+36=0 (tách hạng tử thành nhiều hạng tử)

Question

Toán Lớp 8:  a) x^2+5x-6=0 b) x^2-5x+6=0 c) x^2-3x-18=0 d) x^2-13x+36=0 (tách hạng tử thành nhiều hạng tử)

phuongthaongoc · Answer

Giải đáp:   a)x&isin;{1;-6}   b)x&isin;{2;3}   c)x&isin;{6;-3}   d)x&isin;{4;9}   Lời giải và giải thích chi tiết:   a)x&sup2;+5x-6=0   &hArr;x&sup2;-x+6x-6=0   &hArr;x(x-1)+6(x-1)=0   &hArr;(x-1)(x+6)=0   (1)x-1=0&hArr;x=1   (2)x+6=0&hArr;x=-6   Vậy x&isin;{1;-6}   b)x&sup2;-5x+6=0   &hArr;x&sup2;-2x-3x+6=0   &hArr;x(x-2)-3(x-2)=0   &hArr;(x-2)(x-3)=0   (1)x-2=0&hArr;x=2   (2)x-3=0&hArr;x=3   Vậy x&isin;{2;3}   c)x&sup2;-3x-18=0   &hArr;x&sup2;-6x+3x-18=0   &hArr;x(x-6)+3(x-6)=0   &hArr;(x-6)(x+3)=0   (1)x-6=0&hArr;x=6   (2)x+3=0&hArr;x=-3   Vậy x&isin;{6;-3}   d)x&sup2;-13x+36=0   &hArr;x&sup2;-4x-9x+36=0   &hArr;x(x-4)-9(x-4)=0   &hArr;(x-4)(x-9)=0   (1)x-4=0&hArr;x=4   (2)x-9=0&hArr;x=9   Vậy x&isin;{4;9}

tuyen98 · Answer

y10000 a ) x² + 5x - 6 = 0 <=> x² + 6x - x - 6 = 0 <=> x . ( x + 6 ) . ( x + 6 ) <=> ( x - 1 ) . ( x + 6 ) = 0 <=> ( left[ begin{array}{l}x - 1 = 0 x + 6 = 0 end{array} right. ) <=> ( left[ begin{array}{l}x = 1 x = -6 end{array} right. ) b ) x² - 5x + 6 = 0 <=> x² - 2x - 3x + 6 = 0 <=> x . ( x - 2 ) - 3 . ( x - 2 ) = 0 <=> ( x - 3 ) . ( x - 2 ) = 0 <=> ( left[ begin{array}{l}x - 3 = 0 x - 2 = 0 end{array} right. ) <=> ( left[ begin{array}{l}x = 3 x = 2 end{array} right. ) c ) x² - 3x - 18 = 0 <=> x² - 6x + 3x - 18 = 0 <=> x . ( x - 6 ) + 3 . ( x - 6 ) = 0 <=> ( x + 3 ) . ( x - 6 ) = 0 <=> ( left[ begin{array}{l}x + 3 = 0 x - 6 = 0 end{array} right. ) <=> ( left[ begin{array}{l}x = -3 x = 6 end{array} right. ) d ) x² - 13x + 36 = 0 <=> x² - 9x - 4x + 36 = 0 <=> x . ( x - 9 ) - 4 . ( x - 9 ) = 0 <=> ( x - 4 ) . ( x - 9 ) = 0 <=> ( left[ begin{array}{l}x - 4 = 0 x - 9 = 0 end{array} right. ) <=> ( left[ begin{array}{l}x=4 x=9 end{array} right. )