How do you simplify the expression 7x2−4y+3x2+5y+2 and evaluate it for x+3and y=9?

Question

How do you simplify the expression 7x2−4y+3x2+5y+2 and evaluate it for x+3and y=9?

Jonathan Mckenzie · Accepted Answer

y=−10x2−2  ?x=3−y=−92  ?y=x+3- No real solution  y=9- No real solutions  Explanation:   Assuming this is all equal to 0, we add like terms  10x2+y+2=0  We can then isolate one of the variables, usually y.  y=−10x2−2  To evaluate it for x=3, just plug it into the function to get  y(3)=−10(3)2−2=−10(9)−2=−90−2=−92  To solve for y=x+3 we get  x+3=−10x2−2  10x2+x+5=0  We can use the quadratic formula to get the solutions  −(1)2±(1)2−4(10)(5)2(10)  −1±1−20020  −1±−19920  This results in undefined so there are no real solutions.   For y=9 we do the following  9=−10x2−2  −10x2=11  x2=11−10  x=−1110  This is also undefined, so there are no real solutions.

How do you simplify the expression 7x^{2}-4y+3x^{2}+5y+2 and evaluate it

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