Question
Solve the equation $5x^2 – 3x – 4 = 0$ and give your answer correct to $3$ significant figures:
✓
Answer
We have $5 x^2-3 x-4=0$
Here $a=5, b=-3, c=-4$
$x=\frac{-b \pm \sqrt{b^2-4 a c}}{2 a}$
$=\frac{3 \pm \sqrt{9+4 \times 5 \times 4}}{2 \times 5}$
$=\frac{3 \pm \sqrt{89}}{10}$
$x=\frac{3^{10}+9.43}{10}$ or $x=\frac{3-9.43}{10}$
$\Rightarrow x=\frac{12.43}{10}$ or $x=\frac{-6.43}{10}$
$\Rightarrow x =1.24$ or $x =-0.643$.
Here $a=5, b=-3, c=-4$
$x=\frac{-b \pm \sqrt{b^2-4 a c}}{2 a}$
$=\frac{3 \pm \sqrt{9+4 \times 5 \times 4}}{2 \times 5}$
$=\frac{3 \pm \sqrt{89}}{10}$
$x=\frac{3^{10}+9.43}{10}$ or $x=\frac{3-9.43}{10}$
$\Rightarrow x=\frac{12.43}{10}$ or $x=\frac{-6.43}{10}$
$\Rightarrow x =1.24$ or $x =-0.643$.
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