Question

Tìm x,biết:

a)2x(x-5)-x(3+2x)=26                         b)(x-1)(2x-1)-(x+8)(x-1)=0

c)(x-20)²-x(x-3)=5                               d)x²-11x+18=0

làm nhanh giùm mình nha!

Answer 1

a)2x(x-5)-x(3+2x)=26 

\(VT=-13x\)

\(\Leftrightarrow-13x=26\)

\(\Leftrightarrow x=-2\)

b)(x-1)(2x-1)-(x+8)(x-1)=0

\(VT=x^2-10+9\)

\(\Leftrightarrow x^2-10x+9=0\)

\(\Leftrightarrow x^2-x-9x+9=0\)

\(\Leftrightarrow x\left(x-1\right)-9\left(x-1\right)=0\)

\(\Leftrightarrow\left(x-9\right)\left(x-1\right)=0\)

\(\Leftrightarrow x=9\)hoặc\(x=1\)

c)(x-20)²-x(x-3)=5

\(VT=-\left(37x-400\right)\)

\(\Leftrightarrow-\left(37x-400\right)=5\)

\(\Leftrightarrow400-37x=5\)

\(\Leftrightarrow-37x=-395\)

\(\Leftrightarrow x=\frac{395}{37}\)

d)x²-11x+18=0

\(\Leftrightarrow x^2-2x+9x+18=0\)

\(\Leftrightarrow x\left(x-2\right)-9\left(x-2\right)=0\)

\(\Leftrightarrow\left(x-2\right)\left(x-9\right)=0\)

\(\Leftrightarrow x=2\)hoặc\(x=9\)