Question

GIÚP MIK LM BÀI NÀY NHA :)))))

   Tìm x, biết : 

     a) x( 5 - 3x ) + 3x( x + 1 ) - 40 = 0

     b) ( 12x - 5 )( 4x - 1 ) + ( 3x - 7 )( 1 - 16x ) = 81

MIK CẢM ƠN TRƯỚC NHA. AI LM ĐC THÌ MIK TICK 

Answer 1

\(a,x\left(-3x+5\right)+3x\left(x+1\right)-40=0\)

\(\left(x.-3x\right)+\left(5x\right)+3x\left(x+1\right)-40=0\)

\(-3x^2+5x+\left(3x.x\right)+\left(3x.1\right)-40=0\)

\(-3x^2+5x+3x^2+3x-40=0\)

\(\left(-3x^2+3x^2\right)+5x+3x-40=0\)

\(8x-40=0\)

\(8x=0+40=40\)

\(x=40:8=5\)

Answer 2

a) \(x\left(5-3x\right)+3x\left(x+1\right)-40=0\)

\(\Rightarrow5x-3x^2+3x^2+3x-40=0\)

\(\Rightarrow8x-40=0\)

\(\Rightarrow8x=40\)

\(\Rightarrow x=5\)

b) \(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)

\(\Rightarrow48x^2-12x-20x+5+3x-48x^2-7+112x=81\)

\(\Rightarrow83x=83\)

\(\Rightarrow x=1\)

Answer 3

có làm thì mới có ăn nhé bạn