Question

tìm x biết

b) (2x+3)²-(5x-4) (5x+4) = (x+5)²-(3x-1) (7x+2)-(x²-x+1)

c) (1-3x)²-(x-2) (9x+1)=(3x-4) (3x+4)-9(x+3)²

d) (3x+4) (3x-4)-(2x+5)²=(x-5)²+(2x+1)²-(x²-2x)+(x-1)² cần gắp

Answer 1

Tìm x biết:

b/\(\left(2x+3\right)^2-\left(5x-4\right)\left(5x+4\right)=\left(x+5\right)^2-\left(3x-1\right)\left(7x+2\right)-\left(x^2-x+1\right)\)

<=> \(4x^2 +12x+9-25x^2+16-x^2-10x-25+21x^2+6x-7x-2+x^2-x+1=0\)

<=>0x-1=0

<=>0x=1 (vô lí) (dòng này không cần ghi thêm cũng được)

=> Không có giá trị x nào thỏa mãn

c/ \((1-3x)^2-(x-2)(9x+1)=(3x-4)(3x+4)-9(x+3)^2\)

<=>\(1-6x+9x^2-9x^2-x+18x+2-9x^2+16+9x^2+54x+81=0\)

<=> 65x+100=0

<=> x=\(\dfrac{-20}{13}\)

d/\((3x+4)(3x-4)-(2x+5)^2=(x-5)^2+(2x+1)^2-(x^2-2x)+(x-1)^2\)

<=> \(9x^2-16-4x^2-20x-25-x^2+10x-25-4x^2-4x-1+x^2+2x-x^2+2x-1=0\)

<=> -10x-68=0

<=> x=\(\dfrac{-34}{5}\)