3 years ago

Can you help me, and explain the answer please?

1 answer:

3 0

69:
I know for a fact it can't be (B).
The answer is (A).
Reason: 6 times 9 is 54.

70:
13 is change to 15
13 plus 2 is 15
17 plus 2 is 19
I am 100% sure for question 69, but for question 70 im 100% unsure.

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Solve the following quadratic equation by completing the square ✓3x^2 + 10x + 7✓3 = 0

solmaris [256]

$\sqrt{3}x^2+10x+7\sqrt{3}=0\\\\\sqrt3(x^2+\dfrac{10x}{\sqrt{3}}+7)=0\\\\x^2+\dfrac{10x}{\sqrt{3}}+7=0\\\\x^2+\dfrac{10x}{\sqrt{3}}+\dfrac{25}{3}-\dfrac{25}{3} +7=0\\\\(x+\dfrac{5}{\sqrt{3}})^2 = \dfrac{4}{3}\\\\|x+\dfrac{5}{\sqrt{3}}| = \dfrac{2}{\sqrt{3}}\\\\x_1 = \dfrac{2}{\sqrt{3}}-\dfrac{5}{\sqrt{3}} = -\dfrac{3}{\sqrt{3}} = -\sqrt{3}\\\\x_2 = -\dfrac{2}{\sqrt{3}}-\dfrac{5}{\sqrt{3}} = \dfrac{-7}{\sqrt{3}} = -\dfrac{-7\sqrt{3}}{3}$