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GCSE maths

Using the quadratic formula how do you solve these:
1. X(X+4)=9
2. 2x(x+1)-x(x+4)=11
Im so confused
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davros
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Original post by Lucofthewoods
Using the quadratic formula how do you solve these:
1. X(X+4)=9
2. 2x(x+1)-x(x+4)=11
Im so confused


The first step in each case is to multiply out any brackets and then collect any similar terms together so that you have something that looks like a standard quadratic equation i.e. ax2+bx+c=0ax^2 + bx + c = 0.

Can you get started on this?
Original post by Lucofthewoods
Using the quadratic formula how do you solve these:
1. X(X+4)=9
2. 2x(x+1)-x(x+4)=11
Im so confused


Let me help you with the first one, and then you can try the next one. So we have,

x(x+4)=9  ⟹  x2+4x−9=0x(x+4) = 9 \implies x^2 + 4x - 9 = 0

So, as the previous poster suggested, this is in the form ax2+bx+c=0ax^2 + bx + c = 0 where, a=1,b=4,c=−9a = 1, b = 4, c = -9. Now all you need to do is insert these values into the quadratic formula.
Original post by Paraphilos
Let me help you with the first one, and then you can try the next one. So we have,

x(x+4)=9  ⟹  x2+4x−9=0x(x+4) = 9 \implies x^2 + 4x - 9 = 0

So, as the previous poster suggested, this is in the form ax2+bx+c=0ax^2 + bx + c = 0 where, a=1,b=4,c=−9a = 1, b = 4, c = -9. Now all you need to do is insert these values into the quadratic formula.
okay thanks but where did the 1 come from for the A?
Original post by Lucofthewoods
okay thanks but where did the 1 come from for the A?


It corresponds to the coefficient of the x2x^2 term of the quadratic equation in question.

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