Question

Giup mik voi a

Answer 1

1: Ta có: \(3\left(x+5\right)-2\left(4-3x\right)=7\)

\(\Leftrightarrow3x+15-8+6x=7\)

\(\Leftrightarrow9x=14\)

hay \(x=\dfrac{14}{9}\)

2: Ta có: \(x\left(7-2x\right)+2x\left(x-2\right)=15\)

\(\Leftrightarrow7x-2x^2+2x^2-4x=15\)

\(\Leftrightarrow3x=15\)

hay x=5

3: Ta có: \(2x\left(9x-4\right)-9x\left(2x-3\right)=-38\)

\(\Leftrightarrow18x^2-8x-18x^2+27x=-38\)

\(\Leftrightarrow19x=-38\)

hay x=-2

Answer 2

7: Ta có: \(\left(x-5\right)\left(x+5\right)-\left(x-5\right)^2=30\)

\(\Leftrightarrow x^2-5-x^2+10x-25=30\)

\(\Leftrightarrow10x=60\)

hay x=6

8: Ta có: \(\left(x+2\right)\left(x-2\right)+8=\left(x-1\right)^2\)

\(\Leftrightarrow x^2-4+8=x^2-2x+1\)

\(\Leftrightarrow-2x=3\)

hay \(x=-\dfrac{3}{2}\)