Where does the graph of # y = 3x^2 − 10x − 8# cross the x-axis?

1 Answer
May 28, 2018

Answer:

#x=-2/3,x=4#

Explanation:

#"to find where the graph crosses the x-axis set y = 0"#

#3x^2-10x-8=0#

#"using the a-c method to factor the quadratic"#

#"the factors of the product "3xx-8=-24#

#"which sum to - 10 are - 12 and + 2"#

#"split the middle term using these factors"#

#3x^2-12x+2x-8=0larrcolor(blue)"factor by grouping"#

#color(red)(3x)(x-4)color(red)(+2)(x-4)=0#

#"take out the "color(blue)"common factor "(x-4)#

#(x-4)(color(red)(3x+2))=0#

#"equate each factor to zero and solve for x"#

#x-4=0rArrx=4#

#3x+2=0rArrx=-2/3#
graph{3x^2-10x-8 [-10, 10, -5, 5]}