Toán Lớp 8: tìm x
x.(x+5) – (x – 3)(x + 3) = 6
9 (x + 1)^2 – (3x – 2)(3x + 2) = 10
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Toán Lớp 8: tìm x
x.(x+5) – (x – 3)(x + 3) = 6
9 (x + 1)^2 – (3x – 2)(3x + 2) = 10
Comments ( 2 )
a)
x.(x+5)-(x-3)(x+3)=6
<=>x^2+5x-(x^2-3^2)=6
<=>x^2+5x-(x^2-9)=6
<=>x^2+5x-x^2+9=6
<=>(x^2-x^2)+5x+9=6
<=>5x+9=6
<=>5x=-3
<=>x=-3/5
Vậy x=-3/5
b)
9.(x+1)^2-(3x-2)(3x+2)=10
<=>9.(x^2+2x+1)-[(3x)^2-2^2]=10
<=>9x^2+18x+9-(9x^2-4)=10
<=>9x^2+18x+9-9x^2+4=10
<=>(9x^2-9x^2)+18x+(9+4)=10
<=>18x+13=10
<=>18x=-3
<=>x=-1/6
Vậy x=-1/6