samrand wrote:
In the xy-plane at what point does the graph of y=(x+a)(x+b) intersect the x axis?
1. a+b= -1
2.The graph intersects the y-axis at(0,-6)
Answer:C
X-intercepts of the function
f(x) or in our case the function (graph)
y=(x+a)(x+b) is the value(s) of
x for
y=0. So basically the question asks to find the roots of quadratic equation
(x+a)(x+b)=0.
(x+a)(x+b)=0 -->
x^2+bx+ax+ab=0 -->
x^2+(a+b)x+ab=0.
Statement (1) gives the value of
a+b, but we don't know the value of
ab to solve the equation.
Statement (2) tells us the point of y-intercept, or the value of
y when
x=0 -->
y=(x+a)(x+b)=(0+a)(0+b)=ab=-6. We know the value of
ab but we don't know the value of
a+b to solve the equation.
Together we know the values of both
a+b and
ab, hence we can solve the quadratic equation, which will be the x-intercepts of the given graph.
Answer: C.
Hope it's clear.
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75% (02:24) correct
