Question

Alessandro wrote the quadratic equation –6 = x2 + 4x – 1 in standard form. What is the value of c in his new equation?

Answer 1

ANSWER

$c = 5$

EXPLANATION

A quadratic equation is said to be in standard form when it is in the form

$a {x}^{2} + bx + c = 0$

where a, b, c are real numbers.

The given quadratic equation is

$- 6 = {x}^{2} + 4x - 1$

When we add 6 to both sides, we obtain,

$-6 + 6= {x}^{2} + 4x - 1 + 6$

$\implies \: 0= {x}^{2} + 4x + 5$

Or

$\implies \: {x}^{2} + 4x + 5 = 0$

This is what Alexandra got after he wrote the quadratic equation in standard form.

By comparing this equation to

$a {x}^{2} + bx + c = 0$

we have a=1, b=4 and c=5.