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How do I solve a quadratic equation by competing the square?

How would you solve x 2 +8x+16=81 Show that this can be factorised (x+4) 2 =9 2 Which can then be easily solved by square rooting both sides What if we could now use this method to solve all quadratics?!!? C...
Answered by • Maths tutor
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Solve ((x+2)/3x) + ((x-2)/2x) = 3

Multiple first fraction through by 2 and second fraction through by 3((2x+4)/6x) + ((3x-6)/6x) = (5x-2)/(6x) = 3Expand brackets and isolate x5x-2 = 18x13x = -2x = -2/13
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Answered by Alex B. • Maths tutor
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Let X be a normally distributed random variable with mean 20 and standard deviation 6. Find: a) P(X < 27); and b) the value of x such that P(X < x) = 0.3015.

a) 27 is higher than the mean. So we can simply calculate the z value. z = (27 - 20)/6 ≈ 1.17. Using the table in the formula booklet, we find that P(Z &lt; 1.17) = 0.8790, so P(X &lt; 27) = 0.8790. b) Let's...
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Answered by Maximillian H. • Maths tutor
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5x+3 = 18. What is the value of x?

Take away 3 from both sides to give you : 5x = 15Divide by 5 on both sides to give you : x = 3
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Answered by Joseph B. • Maths tutor
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Solve the quadratic equation: x^2 - 2x - 15 = 0

To solve this, you need to find two factors of -15 that total to give -2. The solution we're looking for is of the for (x + something) (x + something)=0, as you can then solve each bracket to get two results...
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Answered by James H. • Maths tutor
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