Question

1.12 Tìm x, biết:

a) 4x(5x+2) - ( 10x-3)(2x+7)= 133 :

b) 3(6x-5)(4x+1) - (8x+3)(9x-2)= 203

Answer 1

\(a,4x\left(5x+2\right)-\left(10x-3\right)\left(2x+7\right)=133\)
\(20x^2+8x-\left(20x^2+70x-6x-21\right)=133\)
\(20x^2+8x-20x^2-70x+6x+21=133\)
\(-54x+21=133\)
\(-54x=112\)
\(x=\dfrac{112}{54}=\dfrac{28}{13}\)
Vậy \(x=\dfrac{28}{13}\)

\(b, 3\left(6x-5\right)\left(4x+1\right)-\left(8x+3\right)\left(9x-2\right)=203\)
\(3\left(24x^2+6x-20x-5\right)-\left(72x^2-16x+27x-6\right)=203\)
\(72x^2+18x-60x-15-72x^2+16x-27x+6=203\)
\(-53x+6=203\)
\(-53x=197\)
Vậy \(x=\dfrac{-197}{53}\)
- Chúc bạn học tốt ^^-