Tìm x biết:4$x^{2}$+3(2$x^{2}$ +1=2x(5x-7)
tìm x biết: x($x^{2}$ -7)=2x(1/2$x^{2}$ +6)+8
giúp mik vơi mik cần gấp
Tìm x biết:4$x^{2}$+3(2$x^{2}$ +1=2x(5x-7)
tìm x biết: x($x^{2}$ -7)=2x(1/2$x^{2}$ +6)+8
giúp mik vơi mik cần gấp
1)
$4x^2+3(2x^2+1)=2x(5x-7)$
$⇔4x^2+6x^2+3=10x^2-14x$
$⇔4x^2+6x^2-10x^2+14x=-3$
$⇔14x=-3$
$⇔ x=-\frac{3}{14}$
Vậy $S={-\frac{3}{14}}$
2)
$x(x^2-7)=2x(\frac{1}{2}x^2+6)+8$
$⇔x^3-7x=x^3+12x+8$
$⇔x^3-x^3-7x-12x=8$
$⇔-19x=8$
$⇔ x=\frac{-8}{19}$
Vậy $S={\frac{-8}{19}}$
a/ \( 4x^2+3(2x^2+1)=2x(5x-7)\\↔4x^2+6x^2+3=10x^2-14x\\↔10x^2+3=10x^2-14x\\↔10x^2+3-10x^2=-14\\↔3=-14x\\↔-\dfrac{3}{14}=x\)
Vậy \(x=-\dfrac{3}{14}\)
b/ \( x(x^2-7)=2x(\dfrac{1}{2}x^2+6)+8\\↔x^3-7x=x^3+12x+8\\↔x^3-7x-x^3-12x=8\\↔-19x=8\\↔x=-\dfrac{8}{19}\)
Vậy \(x=-\dfrac{8}{19}\)