Question

Use the quadratic formula to solve x2 + 7x + 8 = 0. Estimate irrational solutions to the nearest tenth.

{–12, 5}

{–11.1, –2.9}

{–5.6, –1.4}

{–3.9, 12.1}

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Answer 1

{–5.6, –1.4}

Explanation:

The quadratic formula is
`x=(-b+/-√(b^2-4ac) )/(2a)`. Here a=1, b=7, and c=8.

Substitute and you'll have:

`x=(-b+/-√(b^2-4ac) )/(2a) =(-7+/-√(7^2-4(1)(8)) )/(2(1))=(-7+/-√(49-32) )/(2))`

`(-7+/-√(17) )/(2)`

This approximates as:

`(-7 + 4.123)/(2) , (-7 - 4.123)/(2) \\\\(-3.123)/(2) , (-11.123)/(2)\\-1.6, -5.6`