SOLUTION: Find all x that will make f(x)=0 f(x)=7x^2-2x-4

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Question 442611: Find all x that will make f(x)=0
f(x)=7x^2-2x-4
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

f%28x%29=7x%5E2-2x-4........all x that will make f%28x%29=0
0=7x%5E2-2x-4..use quadratic formula
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+....notice that a=7, b=-2 and c=-4
x+=+%28-%28-2%29+%2B-+sqrt%28+%28-2%29%5E2-4%2A7%2A%28-4%29+%29%29%2F%282%2A7%29+
x+=+%282+%2B-+sqrt%28+4%2B112%29%29%2F14+
x+=+%282+%2B-+sqrt%28+116%29%29%2F14+
x+=+%282+%2B-+10.77%29%2F14+
x1+=+%282+%2B+10.77%29%2F14+
x1+=+%2812.77%29%2F14+
x1+=+0.912.........one solution

x2+=+%282+-+10.77%29%2F14+
x2+=+%28-8.77%29%2F14+
x2+=+-0.63+.........another solution

check: x1+=+0.912+.
f%28x%29=7%280.912%29%5E2-2%280.912%29-4
f%28x%29=7%280.831744%29-1.824-4
f%28x%29=5.822208-1.824-4
f%28x%29=3.99820-4
f%28x%29=4-4
f%28x%29=0