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4 votes
Solve the equation by using the quadratic formula.
8x2 – 2x - 15 =0

User Jsdodgers
by
8.3k points

1 Answer

8 votes

Answer:

x = 3/2 or x = -5/4

Explanation:

Solve for x over the real numbers:

8 x^2 - 2 x - 15 = 0

Using the quadratic formula, solve for x.

x = (2 ± sqrt((-2)^2 - 4×8 (-15)))/(2×8) = (2 ± sqrt(4 + 480))/16 = (2 ± sqrt(484))/16:

x = (2 + sqrt(484))/16 or x = (2 - sqrt(484))/16

Simplify radicals.

sqrt(484) = sqrt(4×121) = sqrt(2^2×11^2) = 2×11 = 22:

x = (2 + 22)/16 or x = (2 - 22)/16

Evaluate (2 + 22)/16.

(2 + 22)/16 = 24/16 = 3/2:

x = 3/2 or x = (2 - 22)/16

Evaluate (2 - 22)/16.

(2 - 22)/16 = -20/16 = -5/4:

Answer: x = 3/2 or x = -5/4

User Slazer
by
9.1k points

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