Hi,

I have a question in regard to a quadratic formula I'm solving.

4(a+b)±√(16(aČ+2ab+bČ)-48ab) / 24

4(a+b)±4√(aČ-ab+bČ) / 24

I don't understand how +2ab became -ab and why -48ab disappeared.

Anyone able to clarify that for me?

Thanks

David

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- Sep 19th 2009, 04:54 AMSplintQuadratic formula 4(a+b)±√(16(aČ+2ab+bČ)-48ab) / 24
Hi,

I have a question in regard to a quadratic formula I'm solving.

4(a+b)±√(16(aČ+2ab+bČ)-48ab) / 24

4(a+b)±4√(aČ-ab+bČ) / 24

I don't understand how +2ab became -ab and why -48ab disappeared.

Anyone able to clarify that for me?

Thanks

David - Sep 19th 2009, 05:03 AMGrandad
Hello Splint

Welcome to Math Help Forum!Just remove the inner brackets inside the square root and simplify:

$\displaystyle \sqrt{\Big(16(a^2+2ab+b^2)-48ab\Big)}$

$\displaystyle =\sqrt{(16a^2+32ab+16b^2-48ab)}$

$\displaystyle =\sqrt{16a^2 -16ab+16b^2}$

$\displaystyle =\sqrt{16}\sqrt{a^2-ab+b^2}$

$\displaystyle =4\sqrt{a^2-ab+b^2}$

Grandad