Solve in brief 3x square - x-4??
2 Answers
Explanation:
(This is a method my teacher developed; it gives the right answer but you should know the other ways to do it before start learning this method)
Multiply the
Then, find the factors that make -12 and add up to -1.
Put the coefficient of
Explanation:
"to solve the quadratic equate to zero and factor"
rArr3x^2-x-4=0
"using the a-c method of factoring"
"the factors of the product "3xx-4=-12
"which sum to - 1 are + 3 and - 4"
"split the middle term using these factors"
3x^2+3x-4x-4=0larrcolor(blue)"factor by grouping"
color(red)(3x)(x+1)color(red)(-4)(x+1)=0
"take out the "color(blue)"common factor "(x+1)
rArr(x+1)(color(red)(3x-4))=0
"equate each factor to zero and solve for x"
x+1=0rArrx=-1
3x-4=0rArrx=4/3