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Solving Equations Using the Quadratic Formula

9.6.4 Solving Equations Using the Quadratic Formula

9.6.4 • Solving Equations Using the Quadratic Formula

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Here is the quadratic formula:

x=−b±b2−4ac2ax=−b±b2−4ac2a

1.

Use the formula to solve the equation x2+9x+8=0x2+9x+8=0.

Compare your answer:

The solutions are -8 and -1.

Apply the quadratic formula for a=1a=1, b=9b=9, c=8c=8:

x=−9±(9)2−4(1)(8)2(1)=−9±492x=−9±(9)2−4(1)(8)2(1)=−9±492, which means

x=−9−72=−8x=−9−72=−8 and x=−9+72=−1x=−9+72=−1.