Question

What is the sum of the two values of $x$ that satisfy the equation $4x^2-3x-1=0$?

• A. $0.75$
• B. $1.25$
• C. $2.5$
• D. $-0.75$
• E. $-1.25$

Answer 1

The correct option is A $0.75$

Solutions of the equation $a{x}^2+bx+c=0$ are given by $\frac{-b\pm \sqrt{b^2-4ac}}{2a}$.
Hence, solutions of the given equation are $\frac{3\pm \sqrt{{(-3)}^2-4\left(4\right)(-1)}}{2\left(4\right)}=\frac{3\pm \sqrt{9+16}}{8}=\frac{3\pm 5}{8}=\frac{3+5}{8}$ or $\frac{-3-5}{8}$
That is $\frac{-1}{4};1$
Sum of these two values are $-\frac{1}{4}+1=-0.25+1=0.75$.