3 years ago

Solve x2-14x+21=0 by completing the square

1 answer:

4 0

$x^2-14x+21=0\\\\x^2-2x\cdot7+7^2-7^2+21=0\\\\(x-7)^2-49+21=0\\\\(x-7)^2-28=0\\\\(x-7)^2=28\iff x-7=-\sqrt{28}\ \vee\ x-7=\sqrt{28}\\\\x=7-\sqrt{4\cdot7}\ \vee\ x=7+\sqrt{4\cdot7}\\\\x=7-2\sqrt7\ \vee\ x=7+2\sqrt7$

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Answer:

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Step-by-step explanation:

Given that:

1/2x-19.7=-4.1

Adding 19.7 on both sides:

1/2x-19.7 + 19.7=-4.1 + 19.7

1/2x = 15.6

Multiplying both sides by 2:

x = 15.6 * 2

x = 31.2

So the number is 31.2

i hope it will help you!

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2 years ago

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pochemuha

Answer:

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