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Maths
GCSE

Prove the quadratic formula for ax^2 + bx + c = 0, where a is non 0 and a,b and c are reals.

By completing the square: ax^2 + bx + c = 0 => x^2 + (bx)/a + c/a = 0 (divide both side by a, since a is non-zero) => (x + b/(2a))^2 + c...

SN
Answered by ShenZhen N. Maths tutor
9079 Views

By factorising, solve the quadratic equation x^2-8x+15=0

First we find two numbers that that add up to -8 and multiply to make 15. In this case the numbers are -3 and -5. This means we can now factorise the quadratic to give (x - 5) (x - 3) = 0. For the above t...

IN
Answered by Ivo N. Maths tutor
3434 Views

How do you use the completing the square method to solve a quadratic equation?

First you need to get the quadratic equation in completed square form. 
This looks like: (x+p)^2 + q 

To put an expression in completed square form you can use this formula: x^2 + 2bx + c = (...

CP
Answered by Caroline P. Maths tutor
3500 Views

Solve 5x - 2 > 3x + 11

When solving inequalities the first step is to put the unknown, in this case x, on the same side of the inequality sign. Remember when you move values to the other side of a sign they change their charge ...

SR
Answered by Sarina R. Maths tutor
5808 Views

The time, T seconds, it takes a water heater to boil a constant mass of water is inversely proportional to the power, P watts, of the water heater. When P is 300, T is 20. What is T when P is 400?

This is a question regarding inverse proportion. This is when one value increases as the other decreases.

For this question, the equation can be written as:

T ∝ 1/P

The directly propo...

SA
Answered by Scott A. Maths tutor
11468 Views

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